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Restoring My 1955 Triumph 6T Thunderbird MotorcycleBY ROGER DUNNICKSEPTEMBER, 2016

2 Restoring My 1955 Triumph 6T

CONTENTS

Introduction .................................................................................................................................................. 7

Understanding Basic Electrical Concepts ................................................................................................... 11 Conventional Flow Versus Electron Flow ........................................................................................... 11 Positive Ground Versus Negative Ground .......................................................................................... 12

Understanding the Wiring and Operation of the 6-Volt System................................................................. 13 PRS8 Ignition/Lighting Switch........................................................................................................... 13 6-Volt Charging System...................................................................................................................... 14

The Alternator ............................................................................................................................... 14The Rectifier.................................................................................................................................. 15

6-Volt Ignition System ........................................................................................................................ 15Normal Running............................................................................................................................ 15Emergency Starting ....................................................................................................................... 15

Understanding the Wiring and Operation of the 12-Volt Upgrade............................................................. 16 12-Volt Charging System.................................................................................................................... 17 12-Volt Electronic Ignition System..................................................................................................... 17

The Stator Plate ............................................................................................................................. 17The Magnetic Rotor ...................................................................................................................... 17The Transistor Box........................................................................................................................ 18The Dual-Output Ignition Coil ...................................................................................................... 18Working Principles ........................................................................................................................ 18

Installing 12-Volt Electrical Load Components ......................................................................................... 18

Installing 12-Volt Charging and Ignition Components .............................................................................. 19 Battery Mounting ................................................................................................................................ 19 Regulator-Rectifier Mounting............................................................................................................. 19 Electronic Ignition System Mounting................................................................................................. 19 Ignition Coil Mounting ....................................................................................................................... 20

Creating a Wiring Diagram for the 12-Volt Upgrade ................................................................................. 20

Choosing a Wiring Harness for the 12-Volt Upgrade................................................................................. 21

Deciding Whether To Use Snap Connectors for the 12-Volt Upgrade....................................................... 21

Deciding Whether To Crimp or Solder for the 12-Volt Upgrade ............................................................... 22

Choosing Fuses for the 12-Volt Upgrade ................................................................................................... 23 What Fuse Rating To Choose ............................................................................................................. 24 When To Fit Additional Fuses ............................................................................................................ 25

Restoring My 1955 Triumph 6T 3

Contents

Gathering Tools and Materials for the 12-Volt Upgrade ............................................................................ 26

Replacing the Regulator-Rectifier for the 12-Volt Upgrade....................................................................... 27

Adding Ground Wires for the 12-Volt Upgrade ......................................................................................... 29 Dedicated Grounds ............................................................................................................................. 30 12-Volt Upgrade Dedicated Grounds.................................................................................................. 30

Battery Ground Connection .......................................................................................................... 30Nacelle Headlamp Assembly Ground Connection........................................................................ 30Regulator-Rectifier Ground Connection ....................................................................................... 31Ignition Coil Ground Connection.................................................................................................. 31Stop-Tail-Lamp Ground Connection............................................................................................. 31

Installing the Wiring Harness for the 12-Volt Upgrade.............................................................................. 31 Wiring Harness Description................................................................................................................ 32 Wiring Harness Modifications ............................................................................................................ 33

Determined Optimal Placement of Wiring Harness...................................................................... 34Removed Wires for the Two Ignition Coil Connections ............................................................... 34Fastened Wiring Harness to the Frame ......................................................................................... 34Performed Major Surgery on the 3-Way Junction......................................................................... 35Added a Blade Fuse Holder and Replaced Female Spade Connectors ......................................... 35Replaced Detachable Plastic Fuse Holder with a Blade Fuse Holder........................................... 36

Connecting Components to the Wiring Harness for the 12-Volt Upgrade ................................................. 36 Transistor Box Connection ................................................................................................................. 37 Dedicated Ground Connections .......................................................................................................... 37 Switch and Headlamp Assembly Connections ................................................................................... 37

Connected the Switch.................................................................................................................... 38Connected the Ammeter and the Hot Side of the Horn................................................................. 39Connected the Headlamp and the Ground Side of the Horn ......................................................... 39Connected the Pilot Lamp ............................................................................................................. 41Connected the Speedometer Lamp................................................................................................ 42

Tail-Lamp and Stop-Lamp-Switch Connections ................................................................................ 42 Alternator Connections ....................................................................................................................... 43 Regulator-Rectifier Connections ........................................................................................................ 44

Testing the 12-Volt Upgrade....................................................................................................................... 45 Testing with No Battery or Lamp Bulbs Installed .............................................................................. 45 Testing with Battery and Lamp Bulbs Installed.................................................................................. 48 Testing with Battery and Lamp Bulbs Installed and Engine Running................................................ 49

Farewell Comments and Suggestions for the 12-Volt Upgrade ................................................................. 51

Wiring Diagrams for the 1955 Triumph 6T and the 12-Volt Upgrade ....................................................... 51


Title Page

FIGURES

1 Wiring Diagram for 1955 Triumph 6T (Ignition Off, Lighting Off).................................................. 52

2 Wiring Diagram for 1955 Triumph 6T (Ignition Off, Pilot Lighting On) .......................................... 53

3 Wiring Diagram for 1955 Triumph 6T (Ignition Off, Headlamp Lighting On) ................................. 54

4 Wiring Diagram for 1955 Triumph 6T (Ignition On, Lighting Off) .................................................. 55

5 Wiring Diagram for 1955 Triumph 6T (Ignition On, Pilot Lighting On)........................................... 56

6 Wiring Diagram for 1955 Triumph 6T (Ignition On, Headlamp Lighting On).................................. 57

7 Wiring Diagram for 1955 Triumph 6T (Emergency Ignition On, Lighting Off) ............................... 58

8 Wiring Diagram for 1955 Triumph 6T (Emergency Ignition On, Pilot Lighting On) ....................... 59

9 Wiring Diagram for 1955 Triumph 6T (Emergency Ignition On, Headlamp Lighting On) .............. 60

10 Wiring Diagram for 1955 Triumph 6T 12-Volt Upgrade................................................................... 61

11 Wassell 12V Electronic Ignition System with EMGO 12V Dual Output Ignition Coil..................... 62


Figures


1.0 Introduction

John, a British motorcycle specialist, and I just finished restoring my 1955 Triumph 6T Thunderbird motorcycle. John did most of the work; I helped rewire the bike. Here are a few photos of the finished product.

7

Introduction


Introduction

I bought the bike in 1967, restored it for the first time in 1979 while serving in the U.S. Army, and then stowed it away in my garage in New Jersey, USA, in 1982. And there it stayed until 2013, at which time I decided to restore it for the second time, except that this time I decided to let a real British motorcycle specialist restore the bike. That’s where John comes in.

In 2012, I retired and moved with my wife to Colorado, USA. In August of 2013, I had my bike shipped from New Jersey straight to John’s shop in Colorado. There, for the next two years, while working on many other vintage British motorcycles, John restored every square inch of my bike. He had the frame and other metal parts sandblasted down to bare metal and then the frame painted black and most everything else painted blue (a somewhat different shade of blue than the factory-original), finished off with several layers of clear coat. He had the twinseat restored to its original factory styling and color. Upon finding scarring on the cylinder walls, he had the cylinders rebored, and installed new pistons and rings. He replaced the Trophy-like headlamp assembly with the factory-original nacelle headlamp assembly. He upgraded the bike to 12 volts and installed an electronic ignition system.

But as much as John enjoys the mechanical aspects of working on vintage British motorcycles, he is still not a big fan of rewiring them. And that’s where I come in. Because of my electronics training in the U.S. Army, John and I decided that I could help with the rewiring. I could not wait to get started!


Introduction

First, I went online and downloaded as many versions of the 1955 Triumph 6T wiring diagram as I could find. Then, I went online and searched for as much advice as I could find on how to rewire a 1955 Triumph 6T from a 6-volt to a 12-volt system. Here are a few of the many well-written and helpful articles that I found online about motorcycle wiring and electrical charging and ignition systems:• “How to Build a Wiring Harness” at

http://www.colorado.edu/physics/EducationIssues/podolefsky/electric_motorcycle_howto_wiring.html

• “Rewiring Your Britbike (2-Wire Alternator) - Positive Ground” at http://www.angelfire.com/biz/snwvlly/bikes/poswire.htm

• “6V to 12V Conversion” at http://php-junder.rhcloud.com/wp-content/uploads/2015/09/6Vto12V.pdf

• “8 Easy Steps to Fit Modern Electrics onto a Classic Bike” at http://www.carolenash.com/insidebikes/biking-tips/1142-8-easy-steps-to-fit-modern-electrics-onto-a-classic-bike

• “Installing a fuse” at http://matchlessclueless.com/electrical/general/installing-a-fuse/

Here is a short list of the vintage Triumph motorcycle manuals that I found online:• “Triumph Workshop Instruction Manual for Models 1945 to 1955” at

http://www.classicbike.biz/triumph/Repair/45-55/45-55TriumphRepair.pdf

• “The Book of the Triumph Twins” at http://www.billymegawatt.com/uploads/6/8/4/6/6846461/pitmans_triumph_twins_book_by_w_c_haycraft.pdf

• “Triumph Replacement Parts Catalogue No.3 Unit Construction 650 c.c. Twins” at http://www.classicbike.biz/triumph/Parts/1960s/65Triumph650ccPartsManual.pdf

• “Lucas Service Manual” at http://www.jerrydoe.com/norton_pdf/Lucas-service.pdf

• “General Service Information” at https://www.britishonly.com/pdf/lucas/LucasServicemanual_noSB519_part3.pdf

To truly understand the mechanical regulation and the emergency starting that were employed by the 1955 Triumph 6T, I decided to create my own version of the 1955 Triumph 6T wiring diagram. Actually, I created nine versions, as shown in Figure 1 on page 52 through Figure 9 on page 60, one for each of the possible PRS8 ignition/lighting switch positions: three ignition switch positions (off, IGN, and EMG) and three lighting switch positions (O, P, and H), for a total of nine possible ignition/lighting switch positions (3 x 3 = 9). I also created wiring diagrams of the 12-volt charging and ignition systems that John applied to my bike, as shown in Figure 10 on page 61 and Figure 11 on page 62. I used the Microsoft Office Visio application to create the 11 diagrams.




http://www.angelfire.com/biz/snwvlly/bikes/poswire.htm

http://www.carolenash.com/insidebikes/biking-tips/1142-8-easy-steps-to-fit-modern-electrics-onto-a-classic-bike

http://matchlessclueless.com/electrical/general/installing-a-fuse/


http://www.billymegawatt.com/uploads/6/8/4/6/6846461/pitmans_triumph_twins_book_by_w_c_haycraft.pdf

http://www.billymegawatt.com/uploads/6/8/4/6/6846461/pitmans_triumph_twins_book_by_w_c_haycraft.pdf

http://www.classicbike.biz/triumph/Parts/1960s/65Triumph650ccPartsManual.pdf

http://www.jerrydoe.com/norton_pdf/Lucas-service.pdf

https://www.britishonly.com/pdf/lucas/LucasServicemanual_noSB519_part3.pdf

http://php-junder.rhcloud.com/wp-content/uploads/2015/09/6Vto12V.pdf

Understanding Basic Electrical Concepts

2.0 Understanding Basic Electrical Concepts

Most of us are familiar with the following basic electrical concepts:• Electric circuit: A closed path in which an electric current flows.

• Voltage (V): An electric potential difference, measured in volts (V), from one point in an electric circuit to another. The voltage rating of a battery describes the potential difference between its positive (+) and negative (-) terminals.

• Current (I): The flow rate of electric charge, measured in amperes (A), in an electric circuit. Alternating current, or AC, is generated by a polarity-changing voltage source such as an alternator; the current flows in one direction and then in the opposite direction at a regular interval. Direct current, or DC, is generated by a polarity-constant voltage source such as a battery or an AC-to-DC rectifier; the current flows in one direction only.

• Resistance (R): The resistance, measured in ohms (Ω), of an electric circuit to current flow. Any component in a circuit, such as a light bulb or even a wire, has resistance associated with it.

• Power (P): The rate of energy consumption, measured in watts (W), in an electric circuit. In a DC circuit, P = V x I.

• Ohm’s Law: An equation, expressed as I = V/R, in which current is directly proportional to the voltage of an electric circuit, and inversely proportional to the resistance of the electric circuit. That is, the more voltage in a circuit, the more current in the circuit, and the more resistance in a circuit, the less current in the circuit.

Note: Ohm’s Law explains why a short-circuit (very low resistance in an electric circuit) results in a very high current.

Some other electrical concepts, however, are somewhat more difficult to comprehend. For me, two such concepts are “conventional flow versus electron flow” and “positive ground versus negative ground.”

2.1 Conventional Flow Versus Electron Flow

Conventional flow assumes that electric charge moves from the positive (surplus of charge) terminal of a voltage source, such as a battery, through the electric circuit and into the negative (deficiency of charge) terminal of the voltage source. Ben Franklin chose this convention during the discovery of electricity in the 1700s.

Electron flow assumes that electric charge moves from the negative terminal of a voltage source, such as a battery, through the electric circuit and into the positive terminal of the voltage source. In the 1800s, scientists discovered that electrons flow from a surplus of electrons at the negative terminal through the circuit to a deficiency of electrons at the positive terminal. The charge on an electron is negative by definition.

By the time that the true direction of current flow (electron flow) was discovered, the nomenclature of “positive” and “negative” had already been so well established in the scientific community that no effort was made to change it. Thus, conventional flow is the notation that most of the world follows.


Understanding Basic Electrical Concepts

Analyzing an electric circuit yields results that are independent of the assumed direction of current flow. In fact, whichever current flow notation is used makes no difference as long as the notation is used consistently. Concepts of voltage, current, resistance, continuity, and even mathematical treatments such as Ohm’s Law remain just as valid with either style of notation.

Although nonpolarized devices, such as switches and incandescent lamps, tolerate currents in either direction with no difference in operation, you should note that polarized devices, such as diodes in an AC-to-DC rectifier, have a preferred or exclusive direction of current. A diode enables an unimpeded flow of current in one direction (low resistance) and blocks current flow in the other direction (high resistance). Because the arrow that represents a diode in a schematic diagram points in the direction of conventional flow (from positive to negative), people like me who think in terms of electron flow view the arrow as pointing against current flow, that is, against the actual flow of electrons. As with analyzing an electric circuit that contains nonpolarized devices, analyzing an electric circuit that contains polarized devices yields the same results as long as the current flow notation is used consistently.

Two last thoughts before moving on to the next topic: People who think in terms of conventional flow perceive the discharging of a battery as current flowing from the positive terminal to the negative terminal, whereas people who think in terms of electron flow perceive the discharging of a battery as current flowing from the negative terminal to the positive terminal. Conversely, people who think in terms of conventional flow perceive the charging of a battery as current flowing into the positive terminal and out of the negative terminal, whereas people who think in terms of electron flow perceive the charging of a battery as current flowing into the negative terminal and out of the positive terminal.

2.2 Positive Ground Versus Negative Ground

Positive ground is also known as “positive battery ground,” “positive chassis ground,” or “positive earth ground.” Negative ground is also known as “negative battery ground,” “negative chassis ground,” or “negative earth ground.”

The grounding of a battery determines where the battery fits within the battery’s electric circuit:• Positive ground: chassis connects to (+) battery (-) connects to load (ignition, lights, horn)

connects to chassis

• Negative ground: chassis connects to load (ignition, lights, horn) connects to (+) battery (-) connects to chassis

For positive ground, the positive terminal of the battery is attached to the chassis and becomes the zero-volt reference point for the circuit. For negative ground, the negative terminal of the battery is attached to the chassis and becomes the zero-volt reference point for the circuit. The “hot” terminal of a battery is the terminal that connects to the load.

Note: A battery’s “hot” terminal is also known as the “feed” terminal, the “live” terminal, or the “power” terminal.

Choosing a positive or negative ground is mostly a matter of convention and standards, although each has its advantages and disadvantages. Positive ground was very common in the 1950s and 60s, especially on 6-volt systems such as the 1955 Triumph 6T. Today, almost all vehicles are negative ground and 12 volts.


Understanding the Wiring and Operation of the 6-Volt System

Positive ground causes corrosion of the surrounding chassis (frame) more so than negative ground, and negative ground causes corrosion of electrical components (wires and connections) more so than positive ground. Clearly, choosing a ground terminal is a trade-off. I chose to stay with positive ground when upgrading my bike to 12 volts.

3.0 Understanding the Wiring and Operation of the 6-Volt System

The wiring and operation of the 6-volt system for the 1955 Triumph 6T are shown in Figure 1 through Figure 9. The nine illustrations differ only in the positions of the PRS8 ignition/lighting switch.

Figure 1, Figure 2, and Figure 3 show that lighting is available even when the bike is not running (ignition switch off). Figure 4, Figure 5, and Figure 6 show how the charging and ignition systems work when the bike is started under normal running conditions (ignition switch set to “IGN”). Figure 7, Figure 8, and Figure 9 show how the charging and ignition systems work when the bike is started under emergency starting conditions (ignition switch set to “EMG”).

3.1 PRS8 Ignition/Lighting Switch

The Lucas PRS8 ignition/lighting switch consists of two independently operated rotary switches, an ignition switch and a lighting switch, that are coupled together. The ignition switch sits on top of the lighting switch. The ignition switch is actuated by an ignition key that is inserted into an ignition shaft, and the lighting switch is actuated by a head knob. The head knob is hollowed out and fits around the ignition shaft.

Each switch has a number of terminal contacts/connectors to which wires can be fastened and secured with slotted screws. The lighting switch has ten terminals, numbered 1 through 11 (9 is omitted). The ignition switch has eight terminals, numbered 12 through 19. In Figure 1 through Figure 9, the thick black lines represent black-wire jumpers that interconnect certain terminals on the switches.

The lighting switch has the following three positions:• “O”: all lights off.

• “P”: pilot (parking) lamp, speedometer lamp, and tail lamp on.

• “H”: headlamp, speedometer lamp, and tail lamp on.

The ignition switch has the following three positions:• Central (between “IGN” and “EMG”): ignition off.

• “IGN”: ignition on for normal running.

• “EMG”: ignition on for emergency starting.



3.2 6-Volt Charging System

The charging system for the 1955 Triumph 6T consists of a 6-volt battery, a Lucas RM14 alternator (rotor and stator), and a Lucas four-plate rectifier pack. The alternator produces AC, the rectifier converts the AC to DC, and the DC charges the battery and provides current to electrical loads such as the ignition coil, lights, and horn.

During normal running conditions, the charging system uses a mechanical means of voltage regulation in which the rate of charge depends on the position of the lighting switch. (Although mechanical regulation is not nearly as good as electronic regulation, it was the only way to regulate a 6-volt battery’s voltage in the 1950s. Electronic regulation came later, with the introduction of the Zener diode and 12-volt systems.) During emergency running conditions, no mechanical regulation is available.

3.2.1 The Alternator

The RM14 alternator has three output wires, produces 1-phase AC, and has a power rating of 120 watts. It consists of a 6-coil laminated stator with the center-bored rotor carried on, and driven by, an extension to the crankshaft. The rotor has a 6-sided steel core, each face of which carries a high-energy permanent magnet that is keyed to a laminated pole-tip.

As shown in Figure 1 through Figure 9, the six alternator coils are connected in pairs to form three pairs of coils, where each pair is connected in series. The first pair, referred to as the “battery charging coils,” connects through a dark green wire to the rectifier and to terminal 7 of the lighting switch. The other two pairs, referred to as the “output control coils,” link together and connect through a mid green wire to terminal 16 of the ignition switch. The remaining terminals of the three pairs of coils link together and connect through a light green wire to the rectifier and to terminal 4 of the lighting switch.

When the engine is started under normal running conditions (ignition switch set to “IGN”) and no lights are in use, the alternator output (in amperes) to the rectifier is only enough to supply the ignition coil and to trickle-charge the battery. When the lighting switch is set to the “P” (pilot, parking) or “H” (headlamp) position, the output to the rectifier increases proportionately.

With the lighting switch in the “O” (off) position, as shown in Figure 4, the “output control coils” are short-circuited through terminals 16, 17, 18, 5, and 4 of the ignition and lighting switches. As a result, due to the interaction of coil flux, which is set up by the heavy current flowing in the short-circuited coils with the flux of the magnetic rotor, the output of the “battery charging coils” decreases. The alternator output to the rectifier is at its minimum value.

With the lighting switch in the “P” position, as shown in Figure 5, the “output control coils” are open (not short-circuited). As a result, due to no interaction of coil flux, the output of the “battery charging coils” increases, to compensate for the additional pilot (parking) lamp, speedometer lamp, and tail lamp loads. The alternator output to the rectifier is at its medium value.



With the lighting switch in the “H” position, as shown in Figure 6, the “output control coils” are connected in parallel with the “battery charging coils” through terminals 16, 17, 18, 6, and 7 of the ignition and lighting switches. As a result, the alternator output to the rectifier increases to its maximum value, to compensate for the additional headlamp, speedometer lamp, and tail lamp loads.

3.2.2 The Rectifier

The Lucas rectifier consists of four plates (coated on one side with selenium) and operates like a non-return valve; it enables current to pass in one direction only. The rectifier converts AC from the alternator to DC, for charging the battery and providing current to electrical loads such as the ignition coil, lights, and horn.

For the 1955 Triumph 6T, the rectifier is bolted to the bike’s frame, directly under the front of the twinseat.

3.3 6-Volt Ignition System

The ignition system for the 1955 Triumph 6T consists of a 6-volt battery, a 6-volt ignition coil, and a distributor. (The contact breaker in the distributor, but not the distributor itself, is shown in Figure 1 through Figure 9.) During emergency running conditions, the ignition system also includes the alternator.

The contact breaker, which is driven (opened and closed) from the inlet cam gear, controls the timing of the high-tension (HT) pulse to the cylinders. When the bike is running, current flows through the contact breaker and the primary winding of the ignition coil. When the contact breaker opens, the current stops, which causes the secondary winding of the ignition coil to generate an HT pulse. The HT pulse routes through an HT cable to the cap and rotor in the distributor, where it is distributed through a spark-plug wire to the spark plug on the appropriate cylinder.

Note: The 1955 Triumph 6T contains a “Speed Twin” (parallel twin) engine, which has a vertically split crankcase that houses a single, central flywheel. The crankpins are “in line,” which causes both pistons to rise and fall together. The cylinders are fired alternately with HT pulses that are spaced evenly at 360 degrees.

3.3.1 Normal Running

During normal running conditions (ignition switch set to “IGN”), as shown in Figure 4, Figure 5, and Figure 6, direct current flows through the contact breaker and the primary winding of the ignition coil. The DC voltage source is the battery when the bike is not running, and is the rectifier when the bike is running.

3.3.2 Emergency Starting

During emergency starting conditions (ignition switch set to “EMG”), as shown in Figure 7, Figure 8, and Figure 9, positive-half-wave-rectified alternating current flows through the contact breaker and the primary winding of the ignition coil; the contact breaker is opened when the current reaches its maximum value. The AC voltage source is the alternator.


Understanding the Wiring and Operation of the 12-Volt Upgrade

(The positive-half-wave-rectified AC to the ignition circuit is through the two pairs of alternator coils previously referred to as the “output control coils.” When the contact breaker is closed, the “output control coils” are short-circuited through terminals 16, 15, and 14 of the ignition switch and a ground-terminal-connecting diode in the rectifier’s bridge [lower-right diode in Figure 7, Figure 8, and Figure 9], which enables a heavy one-way current to build up and flow through the coils. The alternator output to the rectifier is through the single pair of alternator coils previously referred to as the “battery charging coils.”)

For emergency starting, the alternator operates as a magneto and provides current directly to the ignition circuit, to enable a rider to start the bike when the battery is badly discharged or has failed completely. The alternator also continues to trickle-charge the battery through the rectifier.

Correct ignition timing, both electrically and mechanically, is a critical factor for emergency starting. Electrically, the timing position is fixed by the manufacturer, that is, the alternator rotor is keyed to the crankshaft in a position that is consistent with peak voltage and cannot be altered. Mechanically, however, variations in timing can arise. The engine ignition timing must be accurately set to the figures that are specified for the particular motorcycle. In addition, the contact breaker gap must be set to, and maintained at, the specified figure, because any variation in the gap setting will affect the timing position in relation to HT pulse (spark) energy. If the timing at the distributor is advanced or retarded excessively either through a timing error, incorrect contact gaps, or weak automatic advance springs, the contact breaker will not open at the peak of the voltage curve, and consequently the HT pulse will be weak.

Continuous running of the bike with the ignition switch set to “EMG” is not recommended. A rider should turn the ignition switch to “IGN” as soon as possible for the following reason: The contact breaker could become burned and pitted. Also, the lights should not be turned on when running the bike with the ignition switch set to “EMG.”

Emergency starting enables a rider to make short journeys (if absolutely necessary) even if the battery is removed. To do so, the lead that is normally attached to the battery’s negative terminal must be connected to the bike’s chassis. Under these conditions, no lights are available.

4.0 Understanding the Wiring and Operation of the 12-Volt Upgrade

The wiring and operation of the 12-volt upgrade for my 1955 Triumph 6T are shown in Figure 10 and Figure 11. The upgrade enhances the operation and safety of my bike without changing its appearance.

As you can see in Figure 10, when compared to Figure 1 through Figure 9, mechanical regulation has been replaced with electronic regulation, the contact-point ignition system has been replaced with an electronic ignition system, and the emergency starting feature has been dropped. The original PRS8 ignition/lighting switch and the original RM14 alternator have been retained.


Understanding the Wiring and Operation of the 12-Volt Upgrade

Because mechanical regulation and emergency starting are no longer supported, all wires between the PRS8 switch and the alternator have been removed, and the alternator’s output wires have been rewired to provide a continuous maximum output to the regulator-rectifier. Having no alternator connections to the PRS8 switch eliminates the possibility of introducing AC into the DC ignition through the switch, a condition that will not only make the bike run badly but is extremely hard to diagnose without an oscilloscope.

The ignition switch “EMG” position is still available but is not operative. Because the maximum output from the alternator is permanently connected across the regulator-rectifier, the bike can be started with the ignition switch in the “IGN” position regardless of battery condition. The increased output on kick-over is enough to charge the battery sufficiently to start the bike on the third or fourth kick.

4.1 12-Volt Charging System

The charging system for the 12-volt upgrade consists of a Shorai LFX14A1-BS12 lithium-iron 12-volt battery (hereafter referred to as “the 12-volt battery” or just “the battery”), the Lucas RM14 alternator (original rotor and new stator), and a Podtronics 12-volt regulator-rectifier (hereafter referred to as “the regulator-rectifier”). The alternator produces AC, the regulator-rectifier converts the AC to DC, and the DC charges the battery and provides current to electrical loads such as the ignition coil, lights, and horn.

Because all three pairs of alternator coils are permanently connected to the regulator-rectifier, the regulator-rectifier continuously receives full power from the alternator whenever the bike is running. A Zener diode within the regulator-rectifier limits the DC voltage to a preset value and prevents the battery from over-charging.

4.2 12-Volt Electronic Ignition System

The electronic ignition system for the 12-volt upgrade consists of the 12-volt battery; a Wassell distributor/magneto replacement body equipped with a stator plate and a magnetic rotor; a Wassell Micro-MK1 12-volt control unit (hereafter referred to as “the transistor box”); and an EMGO 12-volt dual output ignition coil (hereafter referred to as “the dual-output ignition coil”). The stator plate, magnetic rotor, and transistor box are all part of the Wassell electronic ignition kit called “Ignition Kit Micro-MK1.”

4.2.1 The Stator Plate

The stator plate consists of a pick-up coil and a fixing plate with pole-studs. It is a stationary component that is installed in the Wassell distributor/magneto replacement body, around the magnetic rotor. Two fixing bolts tighten on slots in the fixing plate; the slots provide adjustments for static ignition timing.

4.2.2 The Magnetic Rotor

The magnetic rotor is a round-shaped steel timing device that is mounted on the end of the camshaft in the Wassell distributor/magneto replacement body. It is driven (rotated) from the inlet camshaft wheel and controls the timing of the HT pulse to the cylinders. A fixing bolt is used to hold the magnetic rotor in place.


Installing 12-Volt Electrical Load Components

4.2.3 The Transistor Box

The transistor box is an electronic switch that is contained in a small, lightweight, plastic box.

4.2.4 The Dual-Output Ignition Coil

The dual-output ignition coil provides simultaneous HT sparking, which means that the coil sends an HT pulse to the spark plugs in both cylinders at the same time. The engine will still fire in the correct sequence, with the spurious sparks having no effect.

4.2.5 Working Principles

When the bike is running (ignition switch set to “IGN”), as shown in Figure 11, direct current flows through the transistor box and the dual-output ignition coil. The DC voltage source is the battery when the bike is not running, and is the regulator-rectifier when the bike is running.

When the engine is cranked and a timing mark on the rotating magnetic rotor aligns with a timing mark on the stator plate, a pulse occurs in the stator plate. The pulse routes through two wires to the transistor box, where it triggers the switching off of the current flow through the primary winding of the dual-output ignition coil. When the current is switched off, the secondary winding of the ignition coil generates an HT pulse, which is transferred by the ignition coil through spark-plug wires to the spark plugs on both cylinders.

5.0 Installing 12-Volt Electrical Load Components

John replaced the 6-volt bulbs on my bike with conventional-filament 12-volt bulbs. He retained the original 6-volt horn because it works great in a 12-volt system, really nice and loud.

(Later, when installing the new wiring harness for the 12-volt upgrade, I replaced the 6-volt horn with a 12-volt low-current horn, which is also nice and loud. Reason for replacement: The 6-volt horn has only 1 ohm of resistance, which means that the horn will draw a whopping 12 amperes of current in a 12-volt system! The 12-volt low-current horn has 4 ohms of resistance and therefore will draw only 3 amperes of current in a 12-volt system.)

In a 12-volt system, relative to a 6-volt system, the current that is needed to power the various electrical load components will be halved assuming that you fit like-for-like wattages (for example, fit a 35-watt headlamp bulb at 6 volts with a 35-watt headlamp bulb at 12 volts). Why? Recall that electrical power (in watts) is equal to voltage (in volts) times current (in amperes), that is, P = V x I. Thus, for any given wattage, you can see that doubling the voltage from 6 volts to 12 volts halves the current. And halving the current means that a 12-volt system puts less strain on the wires in the wiring harness.

Someday, I might replace the conventional-filament 12-volt bulbs with positive-ground light-emitting diode (LED) bulbs. LED bulbs are very bright, very robust, and draw less current than conventional bulbs.


Installing 12-Volt Charging and Ignition Components

6.0 Installing 12-Volt Charging and Ignition Components

John replaced the 6-volt lead-acid battery with a Shorai lithium-iron 12-volt battery, the 6-volt rectifier with a Tympanium 12-volt regulator-rectifier, the 6-volt ignition coil with an EMGO 12-volt dual output ignition coil, and the distributor with a Wassell 12-volt electronic ignition system. He installed the stator plate and magnetic rotor of the electronic ignition system into a Wassell distributor/magneto replacement body. Online instructions for installing the Wassell electronic ignition system are located at http://www.totalbikebits.com/wassell/orderpoint/prod_info/WW61495.pdf .

Note: Because of some cracked wires in the stator of the RM14 alternator, John also replaced the stator in the alternator.

As a disclaimer, to the best of my knowledge, John has no connection whatsoever to any of the companies that make the 12-volt products mentioned above. For sure, I have no connection to those companies. Also, as an aside, later, when installing the new wiring harness, I replaced the Tympanium regulator-rectifier with a Podtronics regulator-rectifier, as explained in “Replacing the Regulator-Rectifier for the 12-Volt Upgrade” on page 27.

6.1 Battery Mounting

Because the lithium-iron 12-volt battery is somewhat wider than the 6-volt lead-acid battery, it sits on its right side in the battery box with its front facing left (positive terminal above the negative) so as to maintain a comfortable distance between its terminals and the front battery retaining strap. To cushion the battery and to ensure that it does not move around in the battery box, the battery sits on a rubber pad and is wedged in place with surrounding foam strips.

6.2 Regulator-Rectifier Mounting

The regulator-rectifier is located in the tool side of the battery box, to the right of the battery, and is mounted to the back wall of the battery box. Two fixing bolts secure the regulator-rectifier to the back wall.

The battery box acts as a heat sink for the regulator-rectifier.

6.3 Electronic Ignition System Mounting

The distributor/magneto replacement body is mounted to the crankcase where the distributor was previously mounted. Three fixing bolts secure the replacement body to the crankcase.

The small, lightweight, plastic transistor box of the electronic ignition system is mounted to the inner side wall of the oil tank, just below the twinseat. Two “adhesive on one side, Velcro on the other side” strips, and two pieces of black duct tape, secure the transistor box to the oil tank.


http://www.totalbikebits.com/wassell/orderpoint/prod_info/WW61495.pdf

Creating a Wiring Diagram for the 12-Volt Upgrade

6.4 Ignition Coil Mounting

The dual-output ignition coil is mounted to the rear fender frame brackets (tabs) that are right above the transistor box. Two mounting posts that come with the ignition coil secure the ignition coil to the frame brackets. The mounting posts act as a heat sink, to keep the primary winding of the ignition coil from overheating.

7.0 Creating a Wiring Diagram for the 12-Volt Upgrade

To prepare myself for installing a new wiring harness, I scoured the Internet for wiring diagrams that would help me understand the wiring and operation of my 1955 Triumph 6T’s 6-volt system. I figured that once I gained that understanding, I would know what wiring modifications to make for the 12-volt upgrade.

For authenticity’s sake, I decided to retain the PRS8 switch in the wiring for the 12-volt upgrade. I wanted the PRS8 switch to operate in the 12-volt system just as it did in the 6-volt system, except for emergency starting. For the 12-volt upgrade, setting the PRS8 ignition switch to “EMG” has the same effect as setting the switch to its central (off) position.

Here is the first 6-volt wiring diagram that I found: Figure 68, “Wiring Diagram (5T & 6T)” on page 169 of the “Triumph Workshop Instruction Manual for Models 1945 to 1955” at http://www.classicbike.biz/triumph/Repair/45-55/45-55TriumphRepair.pdf .

To get more details, I consulted other 6-volt wiring diagrams. Here are two diagrams that I found in the “Lucas Service Manual” at http://www.jerrydoe.com/norton_pdf/Lucas-service.pdf :• Figure 76, “Typical 6 volt system using PRS8 switch in a single cylinder machine” on

page 42

• Figure 77, “Typical 6 volt system using 88SA ignition and light switches” on page 43

I also found several 12-volt wiring diagrams, one of which is Figure 79, “Typical 12 volt system (full output)” on page 45 of the “Lucas Service Manual.” The wiring diagram that I created for the 12-volt upgrade (Figure 10) is very much based on that diagram, including the wire colors.

Note: When two colors are indicated for a wire (brown/green, for example), the first is the main color, and the second is the tracer color.

When comparing Figure 79 with other Triumph motorcycle 12-volt wiring diagrams, I noticed a difference in the color of two wires: Figure 79 showed brown wires from the battery’s negative terminal to the ammeter and to the horn, whereas the other wiring diagrams showed brown/blue wires. Because the new wiring harness that I eventually bought contained brown/blue wires, I revisited Figure 10 and changed those two brown wires to brown/blue.

That change was certainly not the last change that I made to Figure 10. Creating a wiring diagram is an iterative process, meaning that the wiring diagram will most likely change many times during the course of installing the wiring harness.



http://www.jerrydoe.com/norton_pdf/Lucas-service.pdf

Choosing a Wiring Harness for the 12-Volt Upgrade

8.0 Choosing a Wiring Harness for the 12-Volt Upgrade

I went shopping online to find a wiring harness for the 12-volt upgrade. After much searching and head scratching, I decided to buy the following wiring harness: “Triumph 3TA, 5TA, 6T Wiring Harness, 12v, 1965-66 1280,” which was described as “a high quality fully braided wiring harness for 12v Triumph 3TA, 5TA and 6T models from 1965 to 1966.” Even though the online illustration appeared to show just a single harness, I fully expected that my purchase would not only include the main harness to the bike’s nacelle headlamp assembly, but would also include the back-end harnesses to the bike’s stop-lamp switch and stop-tail lamp. This expectation just shows how new I am to motorcyle wiring! Anyway, to make a long story short, I was somewhat disappointed when I received the main harness but not the back-end harnesses.

Fortunately, this story has a happy ending. First, I was tickled pink to see that the main harness contained all of the color-coded wires that I needed. Second, I was delighted to learn that John had already installed new harnesses to the stop-lamp switch and the stop-tail lamp, and that the color-coded wires in those harnesses matched the color-coded wires in my wiring diagram. Great! As you might have guessed, I’m a stickler for using properly color-coded wires.

What I still needed was a horn push and dipper switch with the following four color-coded wires: blue, blue/white, blue/red, and brown/black. I found many horn push and dipper switches online but none with those four color-coded wires. Eventually, I did find the following: “Horn Dip Switch Lead, 4 Wire,” which was described as “a replacement lead for handlebar mounted horn/dip switches. 57cm long. Fitted with bullet connector receptacles at one end and bare wires at the other (for connection to the horn/dip switch).” Because the online illustration showed the four color-coded wires that I needed, I bought the 4-wire harness on the spot!

The main harness, the stop-lamp-switch harness, the stop-tail-lamp harness, and the 4-wire horn-push-dipper-switch harness all have crimp-on snap connector terminals.

All of the wires in the harnesses are the Imperial equivalent of 14/0.30 (14 individual strands of copper wire, each 0.30 millimeters in diameter). A 14/0.30 wire has a current rating of eight amperes.

9.0 Deciding Whether To Use Snap Connectors for the 12-Volt Upgrade

Assembling a motorcycle on the factory assembly line necessitates the use of several wiring harnesses and “quick-connect” connectors; the connectors are used to connect the harnesses together to form a complete wiring harness. For British motorcycles, the “quick-connect” connectors are called “snap connectors.” A snap connector consists of a male part, called a “snap connector terminal” or “Lucas type bullet connector” or just “bullet connector,” and a female part, called a “snap connector” or “Lucas female connector.”

Snap connectors enable you to easily take the wiring harness apart. But, as with any inline connector, they also introduce weak spots in your wiring harness. Snap connectors tend to corrode, and corroded connections cause electrical problems.


Deciding Whether To Crimp or Solder for the 12-Volt Upgrade

Because of the corrosion problem, some riders have decided to remove all snap connectors from their wiring harness and crimp or solder the connecting wires together and shrink-tube the connections. Others have decided to keep the snap connectors and periodically pack them with a dab of dialectric tune-up grease to exclude moisture and corrosion. Dialectric tune-up grease is a silicone-based clear gel that does not dry out and does not conduct electricity, but does conduct heat and is very heat resistant.

Two types of snap connector terminals are available: a soldered type and a crimp-on type. As you might have already guessed, soldered snap connector terminals are soldered to wires, and crimp-on snap connector terminals are crimped to wires. Advocates of the crimp-on snap connector terminal highly recommend the TT85 crimping tool, which costs around $60.00.

For the 12-volt upgrade, I decided to keep six snap connectors. I’m confident that the snap connector terminals in the new wiring harness have been installed properly. Now all I have to do is ensure that the snap connector terminals that I install are installed properly.

Because I only need to install two snap connector terminals, I decided to install the soldered type. I’m thinking that if I install them in accordance to the following procedure, they will be installed properly.

(1) Strip 3/8 inch of insulation from the wire; (2) apply electrical soldering flux to the wire; (3) press the wire into the terminal until the end of the wire just barely sticks out of the tip of the terminal; (4) flare the end of the wire; (5) heat the terminal with the soldering iron until the wire is hot enough to melt solder; (6) apply a small amount of rosin/resin-core solder to the tip of the terminal; and (7) clean the terminal (disc brake cleaner works well) to remove all flux residue from the terminal.

In addition, I plan to pack each snap connector with a dab of dialectric tune-up grease.

10.0 Deciding Whether To Crimp or Solder for the 12-Volt Upgrade

I learned most of what I know about crimping by reading “How to Build a Wiring Harness” at http://www.colorado.edu/physics/EducationIssues/podolefsky/electric_motorcycle_howto_wiring.html. The author is Noah Podolefsky.

After reading this very informative and well-written article, I’ve come to believe that good crimps will hold up better than solder, especially in high-vibration environments. Noah sites the following in the American Boat and Yacht Council (ABYC) wiring standards:

Another common misconception dictates that the best of all connections is a soldered connection. However with stranded wire, the solder bonds the individual strands together, making a solid, inflexible wire. ABYC standards prohibit soldering as the sole means of making a connection because the newly solid wire is subject to cracking or breaking through vibration and flexing. A more practical solution is to use a crimp connector described above. Wires should never be joined simply by soldering and taping (or heat shrink); however, if solder is used, use only 60%/40% rosin core or solid solder, soldering after the butt connector is crimped. Acid core solder as used in plumbing may never be used in any electrical wiring.

So if crimping is done right, you do not need to solder. But if you really want to crimp and then solder, have at it. But do not just solder.




Choosing Fuses for the 12-Volt Upgrade

For the 12-volt upgrade, I decided to install insulated and non-insulated crimp terminals and, except for the six snap connectors, decided to use crimp tubes to connect wires. Yet, as previously stated, I decided to install soldered snap connector terminals. Hmmm . . ., do you think that my already having a soldering iron and not having a $60.00 snap-connector-terminal crimping tool had anything to do with that decision?

Anyhow, besides soldering the snap connector terminals, I will solder the 4-wire horn-push-dipper-switch harness to the horn push and dipper switch, and I will solder a red ground wire to the headlamp bulb holder.

11.0 Choosing Fuses for the 12-Volt Upgrade

Most pre-1960 motorcycles, like my 1955 Triumph 6T, were not fitted with a fuse. Whether the omission of a fuse was intentional to save on costs, or whether no one thought of a fuse at the time, is not clear.

A fuse protects a motorcycle’s electric circuit, which is a parallel circuit in which the battery is the voltage source, and each load component is a branch of the parallel circuit. The voltage across each load component is the battery voltage, and the sum of the load-component currents equals the current coming out of and going into the battery.

Without a fuse, excessive current from the battery will damage the battery or the wiring harness or both. The wires would heat up and melt, which could cause an electrical fire. With a fuse, the excessive current will cause the fuse to blow before any damage occurs.

The excessive current is caused by a short-circuit, which is a path of almost no resistance between the terminals of the battery:• If any load component develops a “short” (internal resistance drops close to zero ohms),

the battery current will soar; this condition constitutes a short-circuit in which current travels along an intended path.

• If any wire on the battery’s hot terminal (opposite the ground terminal) becomes abraded and touches the chassis, the battery current will soar; this condition constitutes a short-circuit in which current travels along an unintended path. The unintended path is through the abraded wire and chassis.

Note: A short-circuit along an unintended path is also known as a “short to ground.”

By convention, to protect the electrical system from a short-circuit, a fuse is placed in the hot terminal’s lead, as close to the hot terminal as possible. The latter is important because the short span of wire that connects the hot terminal to the fuse is not protected by the fuse; if that length of wire became abraded and touched the chassis, a short-circuit along an unintended path would occur. The short-circuit would not be detected by the fuse.

Hmmm . . ., I am going to stop here for a minute to share my thoughts with you about the above paragraph. Until just recently, my thinking was that placing the fuse in the hot terminal’s lead or in the ground terminal’s lead had the same result. After all, the current that flows out of one terminal of a battery must flow into the other terminal. And because electrical current moves through wires at a speed only slightly less than the speed of light, a fuse on the ground side will detect a short-circuit as soon as a fuse on the hot side will. In fact, I saw an



advantage of placing the fuse in the ground terminal’s lead: If the short span of wire between the fuse and the ground terminal became abraded and touched the chassis, nothing would happen because the wire and the chassis are at the same voltage: zero volts.

So, for the 12-volt upgrade, I decided to place the main fuse in the ground (positive) terminal’s lead.

And then I spotted the following couple of paragraphs online:If you have a short to ground with a battery, and the fuse doesn’t blow, you have a burnt wiring harness.

Now a lot of Triumph wiring harnesses get burned up. Typically it is the red ground wire from the battery and the damage extends right through the harness. Why didn’t the fuse protect the harness? Was it the wrong size? The fact is even if you had a 1 amp fuse in the system, you still would not have been protected.

Now some of you will immediately recognize the problem and suggest that the fuse should have been put on the ground side of the battery. Well, in 1966 they did just that, but they discovered: If the fuse failed while the bike was running the bike would keep running and damage the rectifier. The next year they changed the harness with the fuse on the feed side of the battery.

Uh-oh! So much for going against convention and standardization. For the 12-volt upgrade, I changed my mind and decided to place the main fuse in the hot (negative) terminal’s lead.

Now, back to the fuse discussion.

11.1 What Fuse Rating To Choose

When determining the rating (size) of the main fuse, you will find the following two equations useful:• Power (in watts) equals voltage (in volts) times current (in amperes): P = V x I.

• Current (in amperes) equals voltage (in volts) divided by resistance (in ohms): I = V/R. This equation is Ohm’s Law.

Begin by computing the maximum electrical load for your motorcycle. Make a list of the various electrical components and their power rating in watts. Then, determine the current in amps by dividing the number of watts by the voltage of your motorcycle’s battery.

If your bike has a low-current horn, you might want to add its current rating to the value calculated above. Otherwise, see “When To Fit Additional Fuses” on page 25. If your bike has a high-current horn, such as a Lucas Altette or Clear Hooter type horn, see “When To Fit Additional Fuses” on page 25.

You need to consider current surges in the electrical load (such as the surge that occurs when initially switching on the lights) when selecting the rating for the main fuse. A good starting point is to over-rate the fuse by 50%, that is, take 1.5 times the calculated current value.

Because fuses come in standard sizes (for example, 1, 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30, and 40 amps for fuses made in the United States), you will need to round off the 50% over-rated current value to the nearest available fuse size. Round down when possible because a smaller fuse will give better protection than a larger one.



Note: Fuse sizes in the United States correspond to fuse “continuous” sizes in Great Britain. For example, a British-made fuse with a “35A/17A” label has a “blow” rating of 35 amps and a “continuous” rating of 17 amps. The closest comparable U.S.-made fuse would be one with a 15 or 20 amp rating.

For the 12-volt upgrade, here is the list of electrical components to be protected by the main fuse:• Headlamp (50 watts)

• Pilot lamp (6 watts)

• Speedometer lamp (3.4 watts)

• Stop lamp (21 watts)

• Tail lamp (6 watts)

• Low-current horn (3 amps, 4 ohms)

• Dual-output ignition coil (3 amps, 4 ohms)

For a total of 86.4 watts and 6 amps. Divide 86.4 watts by 12 volts to get 7.2 amps, and then add 6 amps to get a total of 13.2 amps. Take 13.2 times 1.5 to get 19.8 amps, and then round up to 20. Voila! I chose a Bussmann ATC 20-amp (fast-blow) blade fuse as the main fuse for the 12-volt upgrade.

(Four ground wires in the 12-volt upgrade are 16 American wire gauge [AWG] stranded copper wires, and one ground wire is the Imperial equivalent of 14/0.30 [14 individual strands of copper wire, each 0.30 millimeters in diameter]. A 16-gauge stranded copper wire has a current rating of 20 amps, and a 14/0.30 wire has a current rating of eight amps. All other wires in the 12-volt upgrade, including the brown/blue and brown/white wires, are the Imperial equivalent of 14/0.30.)

With all electrical components in-use except the pilot lamp, stop lamp, and horn, the total current will be 7.95 amps, which can be handled by the 16-gauge wires and the 14/0.30 wires. The intermittent use of the stop lamp or horn will result in a higher total current but only for a short time.

So, occasionally, the current rating of the wiring harness will be exceeded, but only for a short time. Exceeding the current rating of a wire for a short time will not cause the wire to heat up significantly. What will cause the wire to heat up significantly and possibly melt is a short-circuit, which will be prevented by the fuse.

11.2 When To Fit Additional Fuses

Some situations require the fitting of one or more additional fuses to your motorcycle. Adding a separate fuse for a high-current component or a low-current, sensitive component is often a good idea.

If you install a high-current component, such as a Lucas Altette or Clear Hooter type horn, and give it its own fuse, you can reduce the size of the main fuse and therefore provide more protection to the rest of the electrical components. (For the 12-volt upgrade, as an example, if I would give the 3-amp horn its own fuse [say 5 amps], I could reduce the size of the main fuse


Gathering Tools and Materials for the 12-Volt Upgrade

to 15 amps.) You wire the component directly to the hot terminal of the battery and give it its own fuse. The fuse is in parallel with the main fuse.

If you install a low-current, sensitive component, such as an anti-theft alarm, and give it its own fuse (say 1 or 2 amps), you ensure that the component is well protected. You can either wire the component directly to the hot terminal of the battery and give it its own fuse (fuse in parallel with the main fuse), or you can connect the component and its fuse to a point that is already protected by the main fuse (fuse in series with the main fuse).

You should add a fuse to the hot wire of the regulator-rectifier, to protect it from a short-circuit or any other possible threat to its longevity or the longevity of the alternator. (As mentioned earlier, a motorcycle’s electric circuit is a parallel circuit in which the battery is the voltage source, and each load component is a branch of the parallel circuit. What was not mentioned is that the parallel circuit has another voltage source, the regulator-rectifier, which is the primary voltage source when the bike is running. Think of the parallel circuit as a battery at one end, the load components in parallel and in the middle, and the regulator-rectifier at the other end.) Place the fuse as close to the regulator-rectifier as possible. Use the same fuse size as the main fuse.

Note: Of course, when the bike is running, the ultimate voltage source for all load components is the alternator, by way of the regulator-rectifier, assuming that the alternator is functional and turning fast enough.

For the 12-volt upgrade, I added a Bussmann ATC 20-amp (fast-blow) blade fuse to the hot wire (negative terminal) of the regulator-rectifier.

12.0 Gathering Tools and Materials for the 12-Volt Upgrade

I used the following tools to complete the 12-volt upgrade:• Wire cutters

• Automatic wire strippers

• Crimping pliers (for crimping both insulated and non-insulated terminal connectors)

• Heat gun (for shrinking heat-shrink tubing)

• Soldering iron (or gun) (with electrical soldering flux and rosin/resin-core solder)

• Multimeter

• Usual tools such as scissors, screwdrivers, wrenches, utility knife, and so on

I used the following materials to complete the 12-volt upgrade:• Main wiring harness (factory-built)

• 4-wire horn-push-dipper-switch harness (factory-built)

• Spool of 16-gauge red stranded copper wire

• Two black blade fuse holders

• Two Bussmann ATC 20-amp (fast-blow) blade fuses (plus a few spares)

• Black Velcro cable ties


Replacing the Regulator-Rectifier for the 12-Volt Upgrade

• Black nylon cable ties

• Black heat-shrink tubing

• Black plastic electrical tape

• Crimp tubes

• Ring terminal connectors (ring connectors) (non-insulated)

• Spade terminal connectors (spade connectors) (light blue and insulated)

• Single snap connectors (Lucas female connectors)

• Soldered snap connector terminals (Lucas type bullet connectors)

I used crimping to install the terminal connectors, and used crimping and crimp tubes to splice wires together. I covered all spliced wires and non-insulated terminal connections with heat-shrink tubing. I used soldering to install the snap connector terminals.

Note: “covered . . . heat-shrink tubing,” as used here and throughout the rest of the document, means “slide a piece of heat-shrink tubing over the wire splice or the non-insulated terminal connection and then heat the tubing until it forms a tight seal.” Also, to keep things simple, the stripping of insulation from wires for wire splices and wire terminal connections is typically not mentioned in the discussions that follow.

13.0 Replacing the Regulator-Rectifier for the 12-Volt Upgrade

I attribute much of what I know about rewiring my 1955 Triumph 6T to the following online document: “Rewiring Your Britbike (2-Wire Alternator) - Positive Ground” at http://www.angelfire.com/biz/snwvlly/bikes/poswire.htm , authored by Pete Snidal. For the most part, the guidelines in that document are the ones that I followed to complete the wiring for the 12-volt upgrade.

While reading that document, I happened upon the following tidbit:Although I have previously found that Tympaniums, for instance, could be used either way, I just bought two whose Negative Output lines are tied electrically to the case - meaning using Negative Ground or insulating the heat sink from the frame, leaving it hot to the chassis.

. . .

You can check to see if your after-market Regulator/Rectifier unit will permit a choice of grounding by using your multimeter set to “ohms” or “R,” and checking for continuity between the black output wire and the case of the unit. If resistance is infinite, you have a choice, and should stay with the stock grounding for your machine. If Resistance is Zero, you will have to look for another unit, or go to Negative Ground, no longer drinking upstream from the herd.

I immediately started thinking about the Tympanium mounted inside my bike’s battery box. Because I had just removed the fuel tank, twinseat, battery, and battery box in preparation for the rewiring, I had easy access to the Tympanium.


http://www.angelfire.com/biz/snwvlly/bikes/poswire.htm

Replacing the Regulator-Rectifier for the 12-Volt Upgrade

I went to my garage, grabbed the battery box and my multimeter, and went back inside to the living room. After sitting down in my easy chair, I selected the ohms function on the multimeter; selected the X10 range; touched the two probes together and used the Ohm’s Adjust knob to “zero” the reading on the meter; and placed one probe on the dark brown wire of the Tympanium and the other probe on the case of the Tympanium. The meter read a resistance of infinity. Great! My Tympanium was OK.

Sitting there with the Tympanium on my lap and multimeter in hand, I thought what better time than now to test the diodes in the Tympanium’s bridge rectifier? I mean, the multimeter was already set up to read resistance, right?

When testing the forward-direction resistance of a diode, you place the red positive probe on the anode (+) side of the diode, and the black negative probe on the cathode (-) side of the diode. When testing the reverse-direction resistance of a diode, you reverse the probe connections: Place the red positive probe on the cathode (-) side, and the black negative probe on the anode (+) side. The forward-direction resistance should be low, and the reverse-direction resistance should be high.

Upon examining the bridge rectifier in Figure 10, I saw that the two diodes at the positive terminal of the rectifier pointed toward the positive terminal, and that the two diodes at the negative terminal pointed away from the negative terminal. Keep in mind that a diode is represented in a schematic diagram as an arrow that points from the diode’s anode (+) to its cathode (-).

I decided to test the diodes at the positive terminal first. I connected the red positive probe to one of the yellow wires, and the black negative probe to the red wire. I fully expected to see a low resistance reading, but saw a high resistance reading instead. Then, when I reversed the probe connections, I fully expected to see a high resistance reading, but saw a low resistance reading instead. How could that be? Upon testing the remaining three diodes, I experienced the same disappointing results.

What was going on here? Maybe the battery in my multimeter was installed backwards? Upon removing the back panel of the multimeter, I verified that the battery was installed correctly. Maybe the diode arrows in Figure 10 were not oriented correctly? Upon checking other bridge rectifier diagrams, I verified that the arrows were oriented correctly.

I was really stumped. And then a light came on: Could it be that the dark brown wire, which should be attached to the negative terminal, and the red wire, which should be attached to the positive terminal, got switched at the factory? Seemed a little far-fetched, even to me. Wouldn’t the quality control people at the factory catch something like that?

I needed to test the diodes in another Tympanium or another modern regulator-rectifier like the Tympanium, such as the Podtronics. So, I went online and bought another Tympanium and a Podtronics. While waiting for the new units to arrive, I bought another multimeter.

I was very excited when the new units arrived. I was sure that when I tested the diodes in the new units, the results would corroborate what I already suspected: The dark brown and red wires were switched on the original Tympanium. Sadly, I was mistaken. Testing the new units produced the same results.


Adding Ground Wires for the 12-Volt Upgrade

Clearly, I did not understand diodes as well as I thought I did. So, back online I went, to learn more about diodes and how to test them. That’s when I saw this:

Of course, to determine which end of the diode is the cathode and which is the anode, you must know with certainty which test lead of the meter is positive (+) and which is negative (-) when set to the “resistance” or “Ω” function. With most digital multimeters I’ve seen, the red lead becomes positive and the black lead negative when set to measure resistance, in accordance with standard electronics color-code convention. However, this is not guaranteed for all meters. Many analog multimeters, for example, actually make their black leads positive (+) and their red leads negative (-) when switched to the “resistance” function, because it is easier to manufacture it that way!

. . .

For this reason, some digital multimeter manufacturers equip their meters with a special “diode check” function which displays the actual forward voltage drop of the diode in volts, rather than a “resistance” figure in ohms. These meters work by forcing a small current through the diode and measuring the voltage dropped between the two test leads.

You guessed it: Both my multimeters are analog. And when I used the one to check the other, I verified that my red positive probe was indeed negative, and my black negative probe was indeed positive, when I switched to the ohms function. Ho-hum.

I was faced with a dilemma: Should I go with the original Tympanium, or should I replace it with one of the shiny new units? (Both the Tympanium and the Podtronics have the same installation footprint.) The elegantly finned heat sinks on the Podtronics impressed me immensely, so much so that I replaced the Tympanium with the Podtronics.

Since then, I have bought a digital multimeter. And by the way, if you know anybody who wants to buy a Tympanium, I have a couple for sale.

14.0 Adding Ground Wires for the 12-Volt Upgrade

Most pre-1960 motorcycles, like my 1955 Triumph 6T, were not fitted with dedicated ground wires. For a positive-ground system, the bikes relied totally on the chassis as a conductor to carry the current from the positive terminal of the battery to the various electrical components. (For you electron flow enthusiasts, the last sentence should read: For a positive-ground path, the bikes totally relied on the chassis as a conductor to carry the current from the various electrical components to the positive terminal of the battery.)

For a car, the chassis ground system works well because the car’s steel body has a large surface area. (Even though the steel body has more resistivity than copper, its cross-sectional area is much larger than a copper wire’s cross-sectional area, which makes the steel body a better conductor than a copper wire.) For a motorcycle, however, the chassis ground system works less well because the bike’s steel body has a small surface area. In addition, (1) chassis ground paths are not possible through parts of the bike that are isolated from the rest of the bike by insulating materials such as rubber, and (2) chassis ground paths through steering-head bearings or bolt-on sheet metal, such as fenders, often encounter high resistance.

Instead of relying on the chassis for the ground path, you should connect a wire as a ground path to each electrical component. For a positive-ground system, that wire should be red. For a negative-ground system, that wire should be black.


Adding Ground Wires for the 12-Volt Upgrade

14.1 Dedicated Grounds

Choose a grounding point somewhere on the frame (a frame bracket [tab], for example) that is close to the battery and the rectifier. From there, run a ground wire to the ground terminal of the battery; run a ground wire to the headlamp assembly; run a ground wire to the rectifier; run a ground wire to the ignition coil; run a ground wire to the stop-tail lamp; and run a ground wire to any other critical electrical component on your bike. Clean the grounding point to shiny bare metal and use ring connectors and a bolt, nut, and washer to secure the ground wires to the grounding point.

14.2 12-Volt Upgrade Dedicated Grounds

Note: For all wire splices, I crimped crimp tubes to the wire splices and covered the splices with heat-shrink tubing. For all installed ring connectors, I crimped non-insulated ring connectors to the wires and covered the connections with heat-shrink tubing. For all installed spade connectors, I crimped insulated spade connectors to the wires.

For the 12-volt upgrade, I chose the original rectifier mount, under the front of the twinseat, as the grounding point. From there, I ran a red wire to the positive terminal of the battery, a red wire to the nacelle headlamp assembly, a red wire to the regulator-rectifier, a red wire to the dual-output ignition coil, and a red wire to the stop-tail lamp. I cleaned the rectifier mount to shiny bare metal and used ring connectors and a 1/4”-20 x 3/4” cap screw and washer to secure the red wires to the rectifier mount.

Four of the red wires are 16 American wire gauge (AWG) stranded copper wires, and one red wire is the Imperial equivalent of 14/0.30 (14 individual strands of copper wire, each 0.30 millimeters in diameter). The 16-gauge red wires come from a spool of 16-gauge red wire that I bought locally. The 14/0.30 red wire is included in the new wiring harness.

14.2.1 Battery Ground Connection

For the red wire to the positive terminal of the battery, I used a ring connector to connect the wire to the positive terminal.

14.2.2 Nacelle Headlamp Assembly Ground Connection

For the red wire to the nacelle headlamp assembly, I used a ring connector to connect the wire to a handlebar retaining “U” bolt. From there, I used ring connectors to connect red wires to the headlamp bulb holder, the pilot-lamp bulb holder, and the speedometer-lamp bulb holder. For the connection to the headlamp bulb holder, I soldered the wire to the bulb holder’s ground loop connector; for the connection to the pilot-lamp bulb holder, I crimped the wire to the bulb holder’s ground crimp-on connector; for the connection to the speedometer-lamp bulb holder, I crimped the wire to the bulb holder’s ground crimp-on connector.

The red wire to the nacelle headlamp assembly is included in the new wiring harness.


Installing the Wiring Harness for the 12-Volt Upgrade

14.2.3 Regulator-Rectifier Ground Connection

For the red wire to the regulator-rectifier, I used a female spade connector to connect the wire to the male spade connector on the red wire of the regulator-rectifier.

14.2.4 Ignition Coil Ground Connection

For the red wire to the dual-output ignition coil, I spliced the wire to the female spade connector end of the red wire that connects the transistor box to the positive terminal of the ignition coil.

14.2.5 Stop-Tail-Lamp Ground Connection

For the red wire to the stop-tail lamp, I used a ring connector to connect the wire to a stop-tail-lamp mounting bolt. I routed the wire through the same path that the wiring harness to the stop-tail lamp uses: a channel under the rear fender.

15.0 Installing the Wiring Harness for the 12-Volt Upgrade

As mentioned in “Choosing a Wiring Harness for the 12-Volt Upgrade” on page 21, John installed the new harnesses for the stop-lamp switch and the stop-tail lamp. My responsibility was to install the main wiring harness, identified online as “Triumph 3TA, 5TA, 6T Wiring Harness, 12v, 1965-66 1280.”

All of the wires in the main wiring harness are the Imperial equivalent of 14/0.30 (14 individual strands of copper wire, each 0.30 millimeters in diameter). A 14/0.30 wire has a current rating of eight amps.

As corroborated in “What Fuse Rating To Choose” on page 24, 14/0.30 wires are quite suitable for the 12-volt upgrade of my 1955 Triumph 6T. (My bike is running just a headlamp, a pilot lamp, a speedometer lamp, a stop-tail lamp, a low-current horn, and a dual-output ignition coil.) Having said that, I would be most happy if today’s manufacturers of vintage wiring harnesses for British motorcycles would return to the wiring code that was originally used for pre-1971 wiring harnesses:• Thicker wires for the connection to the battery’s negative terminal (brown/blue or brown

wires).

• Thicker wires for the connection to the rectifier’s negative terminal (brown/white, brown, or buff wires).

The thicker wires were the Imperial equivalent of 44/0.30 and had a current rating of 27 amps.

Thicker wires have a higher current rating because they have less resistance: The resistance of a wire is inversely proportional to its cross-sectional area, which means, for example, that if you double the cross-sectional area of a wire, you halve its resistance (and halve its voltage drop). Also, the resistance of a wire is directly proportional to its length, which means, for example, that if you double the length of the wire, you double its resistance (and double its voltage drop).



In Figure 10, notice that the brown/white wire from the regulator-rectifier’s negative terminal routes through terminals 13 and 12 of the PRS8 switch when the switch is set to “IGN,” through a black-wire jumper and another brown/white wire, through the ammeter, and through a brown/blue wire to the battery’s negative terminal. That’s a long run of wire, which could be shortened considerably by connecting the brown/white wire from the regulator-rectifier’s negative terminal directly to the battery’s negative terminal. Doing so would eliminate a lot of resistance and voltage drop, but would also nullify the use of the ammeter: The ammeter would always indicate a negative charge (needle to the left) even when the regulator-rectifier was charging the battery and providing the current to the bike’s electrical loads. Because I like knowing what the charging system is doing, I decided to go with the long run of wire between the regulator-rectifier and the battery.

Also notice in Figure 10 that the horn is wired to bypass the ammeter, so as not to overload the ammeter, to which all other electrical components are connected.

To install the wiring harness, I removed the fuel tank, the twinseat, the headlight unit (with rim attached), the headlamp fixing ring, and the nacelle top. Later in the installation, I also removed the battery and the battery box.

15.1 Wiring Harness Description

The main wiring harness is a cloth-wrapped wiring harness that is intended for a 1966 12-volt Triumph 3TA (350 cc), 5TA (500 cc), or 6T (650 cc). When installed, the wiring harness will run from the nacelle headlamp assembly, along the right side of the frame tube just below the fuel tank, to the battery area on the left side of the bike.

To view the main wiring harness, go to http://britishbikebits.com/cloth-wiring-harness-triumph-3ta-5ta-6t-1966#.VaT4E_lViko . (I bought the wiring harness from another vendor whose online illustration of the harness was far less clear as to what harnesses were included with the main wiring harness.)

At the nacelle end of the wiring harness are two sockets for 88SA ignition and lighting switches, and a 19-inch-long sleeve of polyvinyl chloride (PVC) tubing to protect the cloth-wrapped harness. In the middle are protruding wires for connections to two ignition coils. At the battery end is a 3-way junction: one branch for connections to the rectifier, the battery’s negative terminal, the tail lamp, and the stop-lamp switch; one branch for connections to the Zener diode; and one branch for connections to the alternator. Also, at the 3-way junction is a protruding red wire for connections to the frame grounding point and the battery’s positive terminal. The wiring harness is fitted with all of the terminal connectors that are needed to complete the connections.

Some wires in the wiring harness go from end to end, while others enter and exit the wiring harness along the way. Here is a list of the end-to-end wires:• Brown/blue wire

Starts with a ring connector for a positive (+) ammeter connection, and ends with a detachable plastic fuse holder (fitted with a British 35A/17A glass fuse) and another ring connector for a battery-negative-terminal connection.

• Brown/white wire

Starts with a ring connector for a negative (-) ammeter connection, and ends with a female spade connector for a rectifier-negative-terminal connection.


http://britishbikebits.com/cloth-wiring-harness-triumph-3ta-5ta-6t-1966#.VaT4E_lViko


• Brown/green wire

Starts from the 88SA lighting switch socket, and ends with a snap connector terminal for a tail-lamp connection.

• White wire

Starts from the 88SA ignition switch socket, and meanders through the wiring harness to provide the following connections: two female spade connectors for two ignition-coil-negative-terminal connections; a large female spade connector for a Zener-diode connection; and a snap connector terminal for a stop-lamp-switch connection.

• Red wire

Starts with a snap connector terminal, and meanders through the wiring harness to provide the following connections: a large ring connector for a Zener-diode connection, a female spade connector for a rectifier-positive-terminal connection, and a ring connector for a grounding-point connection and a battery-positive-terminal connection.

Here is a list of enter-and-exit wires:• Black/yellow wire

Starts with a snap connector terminal for a contact-breaker connection, and ends with a female spade connector for an ignition-coil-positive-terminal connection.

• Black/white wire

Starts with a snap connector terminal for a contact-breaker connection, and ends with a female spade connector for an ignition-coil-positive-terminal connection.

• Green/yellow wire

Starts with a snap connector terminal for an alternator-output-wire connection, and ends with a female spade connector for a rectifier-AC-terminal connection.

• White/green wire

Starts with a snap connector terminal for an alternator-common-wire connection, and ends with a female spade connector for a rectifier-AC-terminal connection.

15.2 Wiring Harness Modifications

Because the 12-volt upgrade for my 1955 Triumph 6T is equipped with a PRS8 ignition/lighting switch, an electronic ignition system with a dual-output ignition coil, and a regulator-rectifier complete with Zener diode, I had to make modifications to the main wiring harness. Because my only use of the white wire was to connect the PRS8 ignition switch to the white wire for the transistor box of the electronic ignition system, I shortened the white wire considerably. Also, wherever possible, I replaced the 14/0.30 red wire with individual 16-gauge red wires.



15.2.1 Determined Optimal Placement of Wiring Harness

The first thing that I did was to hold the wiring harness in place on my bike, to determine the optimal placement of the harness. I settled on placing the 3-way junction of the harness a little bit behind and below the original rectifier mount, which put the four rectifier-connection wires and the battery-negative-terminal connection wire within easy reach of the regulator-rectifier and the battery’s negative terminal. (The four wires of the regulator-rectifier pass through a rubber-grommet-lined hole in the back of the battery box.) Unfortunately, though, the placement resulted in the harness protruding a little too far into the nacelle headlamp assembly. No problem. I removed the 19-inch-long sleeve of PVC tubing and used my handy scissors and wire cutters to shorten the harness by about four inches: Snipped away four inches of wrapped cloth and cut off four inches of the brown/blue wire, brown/white wire, brown/green wire, white wire, and red wire, thereby removing the two ring connectors, two 88SA switch sockets, and snap connector terminal from the wires.

I then removed the battery and the battery box and proceeded with the rest of the modifications.

15.2.2 Removed Wires for the Two Ignition Coil Connections

In the middle of the wiring harness, where the black/yellow wire, black/white wire, and white wire protrude for the two ignition coil connections, I used my scissors to snip a three-inch-long slit in the wrapped cloth to reveal the taped bundle of wires underneath. I then snipped and removed the electrical tape; removed the black/yellow and black/white wires and set them aside; and tugged on the white wire to see if I could pull it through the front end of the wiring harness. No luck with the latter: The taping of the wires within the harness held the white wire firmly in place. Ho-hum. So I used my wire cutters to cut and shorten the white wire so that its two ends could be spliced together.

Let me pause here for a minute. I realize that splicing wires together in a wiring harness is not good practice, but I could not get the white wire to budge. If I could have budged the white wire, I would have soldered a 16-gauge white wire to the end of the white wire in the nacelle and pulled the wire through to where I was now. Then, later, when doing major surgery on the 3-way junction of the wiring harness, I would have pulled the 16-gauge white wire through to the junction.

I used a crimp tube to splice the white wires together, and covered the splice with heat-shrink tubing. I then wrapped the three-inch-long section of exposed wire with black electrical tape. And finally, I eased the 19-inch-long sleeve of PVC tubing back onto the harness, which, because of the four-inch shortening of the harness that was done previously, covered the exposed area completely. Nice!

15.2.3 Fastened Wiring Harness to the Frame

I then used black Velcro cable ties and a few black nylon cable ties to fasten the wiring harness to the bike’s frame, with the 3-way junction of the harness a little bit behind and below the original rectifier mount. I really like Velcro cable ties!



15.2.4 Performed Major Surgery on the 3-Way Junction

At the 3-way junction of the wiring harness, I snipped a four-inch-long slit in the wrapped cloth to reveal the taped bundle of wires underneath. I then snipped and removed the electrical tape.

At the 3-way junction, the white wire continues into the Zener-diode branch; wraps around on itself (through a large female spade connector at the end of the Zener-diode branch) back to the junction; and continues into the rectifier branch. The white wire ends with a snap connector terminal for a stop-lamp-switch connection.

At the 3-way junction, the red wire continues into the Zener-diode branch; wraps around on itself (through a large ring connector at the end of the Zener-diode branch) back to the junction; continues into the rectifier branch; wraps around on itself (through a female spade connector at the end of the rectifier branch) back to the junction; and protrudes through the wiring harness. The red wire ends with a ring connector for a grounding-point connection and a battery-positive-terminal connection.

I cut off the Zener-diode branch half way down the branch; set the lower half of the branch aside; and cut off and removed the wrapped cloth from the white and red wires in the upper half of the branch. Doing so reduced the 3-way junction to a 2-way junction consisting of the rectifier branch and the alternator branch.

At the connector end of the rectifier branch, I snipped the wrapped cloth to expose the taped bundle of wires underneath; snipped and removed the electrical tape; pulled the white wire out of the branch and set it aside; cut off the female spade connector on the red wire; and soldered a 14-inch length of 16-gauge red wire to one of the red wires. At the junction end of the rectifier branch, I pulled the two red wires out of the wrapped cloth until the solder joint was about five inches outside the cloth; cut the soldered wires at the solder joint; and set the unattached red wire aside.

I removed the red wire that protruded through the wiring harness and set it aside.

At the 2-way junction, with the white wire pointing down and the two red wires pointing up, I wrapped the section of exposed wire with black electrical tape. I then slid a piece of heat-shrink tubing onto and up the rectifier branch to cover the electrical tape. Because the tubing did not fit snugly, I added more electrical tape and reinstalled the tubing.

15.2.5 Added a Blade Fuse Holder and Replaced Female Spade Connectors

The brown/white wire, green/yellow wire, white/green wire, and red wire in the rectifier branch of the wiring harness will connect the PRS8 ignition switch, alternator, and chassis ground to the regulator-rectifier. The connections will be made by connecting the female spade connectors on these four wires to the male spade connectors on the four wires of the regulator-rectifier.

I cut off the factory-installed female spade connector from the brown/white wire and used a crimp tube to splice a blade fuse holder to the brown/white wire; I covered the splice with heat-shrink tubing. I then crimped an insulated female spade connector to the other end of the blade fuse holder. Splicing the blade fuse holder to the brown/white wire essentially lengthened the brown/white wire by six inches, which made the fuse holder easily accessible through the battery box.


Connecting Components to the Wiring Harness for the 12-Volt Upgrade

I placed a Bussmann ATC 20-amp (fast-blow) blade fuse in the fuse holder.

I cut off the factory-installed female spade connectors from the green/yellow and white/green wires and crimped new insulated female spade connectors to those two wires and to the red wire.

I bundled the green/yellow wire, white/green wire, red wire, and brown/green wire together with black electrical tape. I then slid a piece of heat-shrink tubing over the electrical tape such that the tubing covered the electrical tape and touched up against the protruding brown/white wire. Because the tubing did not fit snugly, I added more electrical tape and reinstalled the tubing.

15.2.6 Replaced Detachable Plastic Fuse Holder with a Blade Fuse Holder

The brown/blue wire in the rectifier branch of the wiring harness ends with a detachable plastic fuse holder and a ring connector for connecting to the battery’s negative terminal.

I cut out the fuse holder and used two crimp tubes to splice in a blade fuse holder. The splice on the non-battery side of the fuse holder was a three-wire splice: It included the hot brown wire in the stop-lamp-switch harness that John installed. I covered the splices with heat-shrink tubing.

I placed a Bussmann ATC 20-amp (fast-blow) blade fuse in the fuse holder.

16.0 Connecting Components to the Wiring Harness for the 12-Volt Upgrade

When I finished modifying the main wiring harness, I had a brown/blue, brown/white, brown/green, white, and red wire running from the nacelle to the original rectifier mount, where the white wire exited the harness to provide an ignition-switch connection for the transistor box of the electronic ignition system, and the red wire exited the harness to provide a ground connection for the nacelle.

The brown/blue, brown/white, and brown/green wires continued through the rectifier branch of the wiring harness to the battery area, where the brown/blue wire provided an ammeter connection for the battery’s negative terminal, the brown/white wire provided an ignition-switch connection for the regulator-rectifier’s negative terminal, and the brown/green wire provided a lighting-switch connection for the tail lamp.

I also had a green/yellow and white/green wire running from the alternator through the alternator branch and rectifier branch of the wiring harness to the regulator-rectifier, where the two wires provided an alternator connection for the regulator-rectifier’s AC terminals. And, finally, I had a red wire running from the original rectifier mount through the rectifier branch of the wiring harness to the regulator-rectifier, where the wire provided a ground connection for the regulator-rectifier’s positive terminal.

The next thing to do was to connect these wires to the components that they served.



16.1 Transistor Box Connection

At the original rectifier mount, I cut the white wire to the appropriate length, used a crimp tube to splice the white wire to the white wire for the transistor box of the electronic ignition system, and covered the splice with heat-shrink tubing. The other electrical connections from the distributor/magneto replacement body to the transistor box to the dual-output ignition coil to the spark plugs were completed by John. See Figure 11 and “12-Volt Electronic Ignition System” on page 17 for more information about the installed electronic ignition system for the 12-volt upgrade.

16.2 Dedicated Ground Connections

At the original rectifier mount, I cut the two red wires to the appropriate length, crimped a non-insulated ring connector to each of the wires, covered each connection with heat-shrink tubing, and connected the ring connectors to the rectifier mount. See “12-Volt Upgrade Dedicated Grounds” on page 30 for more information about the installed dedicated grounds for the 12-volt upgrade.

16.3 Switch and Headlamp Assembly Connections

Figure 10 shows the PRS8 ignition/lighting switch connections for the 12-volt upgrade. The following list identifies the in-use switch terminals and where they connect:• Terminal 1: red/black wire to the pilot lamp.

I used the red/black wire that was part of a previously bought horn push and dipper switch to connect terminal 1 to the pilot-lamp bulb holder. (When viewing the horn push and dipper switch online, I thought that I saw the four color-coded wires that I needed [blue, blue/white, blue/red, and brown/black], but what I saw as a blue/red wire and a brown/black wire were in fact a red/black wire and a brown wire.)

• Terminal 2: brown/white wire to the negative (-) side of the ammeter; and black-wire jumper to terminal 12.

I used the four-inch brown/white wire that I had previously cut off the main wiring harness to connect terminal 2 to the negative terminal of the ammeter.

• Terminal 3: blue wire to the horn push and dipper switch, and from that switch to the headlamp main beam and dip beam.

I used the 4-wire horn-push-dipper-switch harness that I had previously bought online to connect (1) terminal 3 (blue wire) to the horn push and dipper switch on the left handlebar, (2) the dipper switch to the main beam (blue/white wire) and dip beam (blue/red wire) of the headlamp bulb holder, and (3) the horn push switch to the ground terminal (brown/black wire) of the horn.

• Terminal 8: brown/green wire to tail lamp; black-wire jumper to terminal 11.

I used the brown/green wire in the main wiring harness to connect terminal 8 through a snap-connector connection in the battery area to the brown/green wire in the stop-tail-lamp harness.

• Terminal 10: black-wire jumper to terminal 12.



• Terminal 11: brown/green wire to speedometer lamp; black-wire jumper to terminal 8.

I used the brown/green wire of a newly bought speedometer-lamp bulb holder to connect terminal 11 to the speedometer-lamp bulb holder.

• Terminal 12: black-wire jumpers to terminals 2 and 10.

• Terminal 13: brown/white wire to negative (-) terminal of regulator-rectifier.

I used the brown/white wire in the main wiring harness to connect terminal 13 to the negative terminal of the regulator-rectifier.

• Terminal 14: white wire to white wire for transistor box of electronic ignition system.

I used the white wire in the main wiring harness to connect terminal 14 to the white wire for the transistor box.

In addition, I used the brown/blue wire in the main wiring harness to connect the positive (+) side of the ammeter to the battery’s negative terminal, and used the brown/blue wire in a two-wire horn subharness that came with the main wiring harness to connect the positive terminal of the ammeter to the horn.

A “hot wire” is any wire that has electric potential relative to chassis ground. For the 12-volt upgrade, the brown/blue and brown/white wires are hot wires, and the brown/green, red/black, blue, and white wires are hot wires when the PRS8 ignition/lighting switch is turned on.

Terminal 2 on the lighting switch is the battery’s hot wire connection to the switch, and terminal 13 on the ignition switch is the regulator-rectifier’s hot wire connection to the switch. When the ignition switch is set to “IGN,” terminals 2, 10, 12, 13, and 14 are all hot terminals.

16.3.1 Connected the Switch

I bought online a new (rebuilt) PRS8 ignition/lighting switch and a PRS8 switch alloy base plate (with a black-colored center and silver-colored “H,” “P,” and “O” letters). Already installed on the PRS8 switch were a white/red wire to terminal 2 and several black-wire jumpers that interconnected certain switch terminals.

I removed the white/red wire and all but three black-wire jumpers: Retained black-wire jumpers from terminal 2 to terminal 12, from terminal 12 to terminal 10, and from terminal 8 to terminal 11. I then installed the four-inch brown/white wire to terminal 2.

For any terminal that contained two wires, for example, the brown/white wire and the black wire in terminal 2, I twisted the two wires together and tinned them lightly with solder to ensure that both wires stayed put when securing them in the terminal with the terminal’s slotted screw.



I placed the nacelle top on top of the left and right nacelle covers and over the handlebars; hand-held the PRS8 switch directly under the switch mounting hole in the nacelle top; and oriented the switch to its mounting position (terminal 2 to the front of the nacelle and slightly toward the ammeter). I then installed the following wires from the main wiring harness to the switch:• Brown/green wire (tail lamp) to terminal 8.

• Brown/white wire (regulator-rectifier’s negative terminal) to terminal 13.

• White wire (transistor box) to terminal 14.

When finished, I laid the PRS8 switch in the nacelle.

16.3.2 Connected the Ammeter and the Hot Side of the Horn

The ammeter has a negative (-) terminal and a positive (+) terminal, both of which are threaded and have a fixing nut and washer. When looking into the front of the nacelle, the negative terminal is to the right, and the positive terminal is to the left.

I crimped a non-insulated ring connector to the four-inch brown/white wire from the PRS8 switch, covered the connection with heat-shrink tubing, and connected the ring connector to the negative terminal of the ammeter. With this connection in place, the negative terminal of the regulator-rectifier connects through terminals 13, 12, and 2 of the PRS8 switch to the negative terminal of the ammeter when the PRS8 switch is set to “IGN.”

I crimped a non-insulated ring connector to the brown/blue wire in the main wiring harness, covered the connection with heat-shrink tubing, and connected the ring connector to the positive terminal of the ammeter. With this connection in place, the negative terminal of the battery connects to the positive terminal of the ammeter.

I also connected a second brown/blue wire to the positive terminal of the ammeter, to serve as the hot wire for the horn. I cut the second brown/blue wire to the appropriate length; crimped a non-insulated ring connector to the one end of the wire; covered the connection with heat-shrink tubing; crimped an insulated female spade connector to the other end of the wire; connected the ring connector to the positive terminal of the ammeter; and connected the female spade connector to one of the two male spade connectors on the horn.

Note: In most cases, horns are not polarity-specific, meaning that you can connect the hot wire to either of the two terminals on the horn, and connect the ground wire from the handlebar-mounted horn push switch to the remaining terminal. Also, as an aside, I replaced the original 6-volt horn on my bike with a 12-volt low-current (3-amp, 4-ohm) horn.

16.3.3 Connected the Headlamp and the Ground Side of the Horn

I used the 4-wire horn-push-dipper-switch harness to connect terminal 3 of the PRS8 switch to the dipper switch (blue wire) on the horn push and dipper switch; the dipper switch determines whether the headlamp main beam (blue/white wire) or the headlamp dip beam (blue/red wire) is the hot wire when the PRS8 switch is set to “H.” I also used the 4-wire horn-push-dipper-switch harness to connect the push switch on the horn push and dipper switch to the horn (brown/black wire).



To view the 4-wire horn-push-dipper-switch harness, go to http://www.classicmotorcyclespares.com/index.php/default/electrical/wiring/triumph-wiring-harnesses/horn-dip-switch-lead-4-wire.html#Wiring.

Specifically, I performed the following tasks:1. Removed the plastic dipper switch from the metal shell of a previously bought horn push

and dipper switch that did not have the four color-coded wires that I needed.

2. Laid the dipper switch on a short wooden board on my workbench, with the dipper-switch handle to my right and the four wires facing up.

3. Desoldered and removed the four wires from the dipper switch.

4. Soldered the 4-wire horn-push-dipper-switch harness to the dipper switch in accordance to the following procedure:

a. Wrapped a rubber band around the short wooden board and the dipper switch to hold the switch in place.

b. With the snap-connector ends of the 4-wire horn-push-dipper-switch harness to my left, placed the bare-wire ends of the harness on top of the dipper switch, with the blue/red wire closest to me, then the blue wire, then the brown/black wire, and then the blue/white wire.

c. Cut each wire as needed so that its end was centered over its associated soldering point on the dipper switch.

d. Stripped 1/4 inch of insulation from each wire and used needlenose pliers to put a 1/8-inch-long, 90-degree downward bend in the wire.

e. Placed the downward tip of each wire into its associated soldering point on the dipper switch.

f. For each wire, wrapped a rubber band around the short wooden board and the wire to hold the wire tight against its associated soldering point on the dipper switch.

g. Applied electrical soldering flux to each wire.

h. Heated each soldering point with the soldering iron until the associated wire was hot enough to melt solder, and then applied a small amount of rosin/resin-core solder to the wire.

i. Cleaned each wire (disc brake cleaner works well) to remove all flux residue from the wire.

5. Removed the rubber bands and placed the rewired dipper switch into its metal shell.

6. Installed the rewired horn push and dipper switch on the left handlebar, ensuring that all four wires were seated in the notch opening of the switch and not pinched between the switch and the handlebar; removed the four snap connectors from the horn-push-dipper-switch harness; and threaded the harness through the nacelle handlebar cutout and out the front of the nacelle.

7. Shortened the horn-push-dipper-switch harness until only about four inches of harness stuck out the front of the nacelle: Snipped away three inches of the harness’s PVC tubing and cut off three inches of each of the harness’s four wires, thereby removing the four snap connector terminals from the wires.


http://www.classicmotorcyclespares.com/index.php/default/electrical/wiring/triumph-wiring-harnesses/horn-dip-switch-lead-4-wire.html#Wiring

http://www.classicmotorcyclespares.com/index.php/default/electrical/wiring/triumph-wiring-harnesses/horn-dip-switch-lead-4-wire.html#Wiring


8. Inside the nacelle, about three inches from where the horn-push-dipper-switch harness enters the nacelle through the nacelle handlebar cutout, snipped a one-inch-long slit in the harness’s PVC tubing and pulled the blue and brown/black wires out through the slit.

9. Cut the blue wire to the appropriate length and connected it to terminal 3 on the PRS8 switch.

10. Cut the brown/black wire to the appropriate length; crimped an insulated female spade connector to its end; and connected the female spade connector to the unconnected male spade connector on the horn.

11. From the blue/white and blue/red wires of a newly bought headlamp bulb holder, removed the two snap connectors and cut off the two snap connector terminals.

12. Used a crimp tube to splice the blue/white wire of the headlamp bulb holder to the blue/white wire in the horn-push-dipper-switch harness, and covered the splice with heat-shrink tubing.

13. Used a crimp tube to splice the blue/red wire of the headlamp bulb holder to the blue/red wire in the horn-push-dipper-switch harness, and covered the splice with heat-shrink tubing.

14. Cut a 12-inch length of 16-gauge red wire; crimped a non-insulated ring connector to one end of the wire; covered the connection with heat-shrink tubing; connected the ring connector to the handlebar retaining “U” bolt to which a red wire from the original rectifier mount was connected; and threaded the other end of the wire through the one-inch-long slit in the PVC tubing of the horn-push-dipper-switch harness and out the end of the harness. (See “Nacelle Headlamp Assembly Ground Connection” on page 30 for more information about the installed dedicated ground for the nacelle headlamp assembly.)

15. Cut the red wire to the appropriate length, and soldered the wire to the headlamp bulb holder in accordance to the following procedure:

a. Stripped 3/4 inch of insulation from the wire and wrapped the bare wire around the ground loop connector on the headlamp bulb holder.

b. Applied electrical soldering flux to the wire.

c. Heated the ground loop connector and wire with the soldering iron until the wire was hot enough to melt solder.

d. Applied a small amount of rosin/resin-core solder to the wire.

e. Cleaned the wire (disc brake cleaner works well) to remove all flux residue from the wire.

16.3.4 Connected the Pilot Lamp

I replaced the pilot-lamp bulb holder with a new bulb holder, which had a brown/green wire that ended with a snap connector terminal. (The properly color-coded wire for my pilot lamp connection is red/black.) I used the red/black wire that was part of a previously bought horn push and dipper switch to connect the pilot-lamp bulb holder to the PRS8 switch.

I connected one end of the red/black wire to terminal 1 on the PRS8 switch, and threaded the other end of the wire through the one-inch-long slit in the PVC tubing of the horn-push-dipper-switch harness and out the end of the harness.



I cut the red/black wire to the appropriate length so that the wire stuck out the front of the nacelle four more inches than the blue/white and blue/red wires in the horn-push-dipper-switch harness; cut the brown/green wire on the pilot-lamp bulb holder one inch from its connection on the bulb holder; used a crimp tube to splice the one-inch brown/green wire to the red/black wire; and covered the splice with heat-shrink tubing.

I cut a five-inch length of 16-gauge red wire; crimped one end of the wire to the ground crimp-on connector on the pilot-lamp bulb holder; covered the connection with heat-shrink tubing; used a crimp tube to splice the other end of the wire to the red wire that was soldered to the headlamp bulb holder; and covered the three-way splice with heat-shrink tubing. (See “Nacelle Headlamp Assembly Ground Connection” on page 30 for more information about the installed dedicated ground for the nacelle headlamp assembly.)

16.3.5 Connected the Speedometer Lamp

I replaced the speedometer-lamp bulb holder with a new bulb holder, which had a brown/green wire (the properly color-coded wire for my speedometer lamp connection) that ended with a snap connector terminal. I used the brown/green wire to connect the speedometer-lamp bulb holder to the PRS8 switch.

I cut off the snap connector terminal from the brown/green wire and connected the wire to terminal 11 on the PRS8 switch.

I cut a six-inch length of 16-gauge red wire; crimped one end of the wire to the ground crimp-on connector on the speedometer-lamp bulb holder; covered the connection with heat-shrink tubing; crimped a non-insulated ring connector to the other end of the wire; covered the connection with heat-shrink tubing; and connected the ring connector to the handlebar retaining “U” bolt to which a red wire from the original rectifier mount was connected. (See “Nacelle Headlamp Assembly Ground Connection” on page 30 for more information about the installed dedicated ground for the nacelle headlamp assembly.)

16.4 Tail-Lamp and Stop-Lamp-Switch Connections

The following connections occur in the battery area between the main wiring harness, the stop-tail-lamp wiring harness, and the stop-lamp-switch wiring harness:• A snap-connector connection between the brown/green wire in the rectifier branch of the

main wiring harness to the brown/green wire in the stop-tail-lamp wiring harness.

• A snap-connector connection between the brown wire in the stop-lamp-switch wiring harness to the brown wire in the stop-tail-lamp wiring harness.

Using a snap connector packed with a dab of dialectric tune-up grease, I connected the brown/green wire in the rectifier branch of the main wiring harness to the brown/green wire in the stop-tail-lamp wiring harness.

Using another snap connector packed with a dab of dialectric tune-up grease, I connected the brown wire in the stop-lamp-switch wiring harness to the brown wire in the stop-tail-lamp wiring harness.

I ensured that all four snap connector terminals were fully seated and tightly fitted in the snap connectors.



Note: For the two snap connectors at the stop-tail-lamp assembly, I packed the snap connectors with dabs of dialectric tune-up grease and ensured that all four snap connector terminals were fully seated and tightly fitted in the snap connectors.

16.5 Alternator Connections

For reference, here are the transitional color-coding schemes for the 3-wire 1-phase RM13/RM14/RM15 alternator:

light green -> light green -> green/white -> white/greenmid green -> green/yellow -> green/yellow -> green/yellowdark green -> dark green -> green/black -> green/black

Because the original colors (light green, mid green, and dark green) discolored with age, they eventually became indistinguishable from one another. To assist in wire identification, the light green was changed to green/white and then to white/green; the mid green was changed to green/yellow; and the dark green was changed to green/black. The RM14 alternator in my bike uses the “green/white, green/yellow, green/black” color-coding scheme, but to keep things simple, I identify the “green/white” wire as “white/green” in Figure 10 and in the discussion that follows.

As shown in Figure 10, the six coils of the RM14 alternator are connected in pairs to form three pairs of coils, where each pair is connected in series. One pair connects to a green/black wire, and two pairs connect to a green/yellow wire. The remaining terminals of the three pairs link together and connect to a white/green wire.

For the 12-volt upgrade, I rewired the alternator’s 3-wire output to just two wires, a green/yellow wire and a white/green wire, where the green/yellow wire is spliced to the original green/yellow and green/black output wires. I then soldered snap connector terminals to the green/yellow and white/green wires, for connection to the regulator-rectifier through the green/yellow and white/green wires in the alternator branch and rectifier branch of the main wiring harness. The rewiring of the alternator’s output will provide a continuous maximum output to the regulator-rectifier’s AC terminals.

Specifically, I performed the following tasks:1. Considerably shortened the alternator’s 3-wire output cable.

2. Snipped away four inches of wrapped cloth on the 3-wire output cable, unraveled the green/yellow, green/black, and white/green wires, and cut two inches off of the green/yellow and green/black wires.

3. Used a crimp tube to splice the green/yellow and green/black wires in the 3-wire output cable to the two-inch green/yellow wire that I cut off in step 2.

4. Covered the three-way splice with heat-shrink tubing and wrapped the tubing with several layers of black electrical tape.

5. Soldered a snap connector terminal to the green/yellow wire and to the white/green wire in accordance to the following procedure:

a. Stripped 3/8 inch of insulation from the wire.

b. Applied electrical soldering flux to the wire.



c. Pressed the wire into the terminal until the end of the wire just barely stuck out of the tip of the terminal.

d. Flared the end of the wire.

e. Heated the terminal with the soldering iron until the wire was hot enough to melt solder.

f. Applied a small amount of rosin/resin-core solder to the tip of the terminal.

g. Cleaned the terminal (disc brake cleaner works well) to remove all flux residue from the terminal.

6. Slid a four-inch piece of heat-shrink tubing over the snap connector terminals and onto the alternator output cable such that the tubing covered the already taped and shrink-tubed three-way splice and overlapped the wrapped cloth on the output cable by about an inch.

7. Heated the heat-shrink tubing until it closed tightly around the three-way splice and the output cable.

8. Using two snap connectors packed with dabs of dialectric tune-up grease, connected the green/yellow and white/green wires to the green/yellow and white/green wires in the alternator branch of the wiring harness.

9. Ensured that all four snap connector terminals were fully seated and tightly fitted in the snap connectors.

10. Used a black Velcro cable tie to fasten the alternator branch of the wiring harness to the bottom of the central upright frame tube, to ensure that the alternator’s output cable could not come in contact with the rear (secondary) chain.

Note: I also used a black Velcro cable tie to fasten the cable between the distributor/magneto replacement body and the transistor box to the bottom of the central upright frame tube, to ensure that the cable could not come in contact with the rear chain.

In hindsight, I am thinking that maybe, just maybe, I should have connected the alternator’s rather long output cable directly to the regulator-rectifier. Specifically, I could have (1) completed the three-way splice of the alternator’s green/yellow and green/black wires at a point within easy reach of the regulator-rectifier, (2) crimped insulated female spade connectors to the green/yellow and white/green wires for connection to the regulator-rectifier’s AC terminals, (3) cut off the alternator branch of the wiring harness, and (4) pulled the green/yellow and white/green wires out of the rectifier branch of the wiring harness. Having done so would have eliminated two snap connectors and shortened the wiring path by about a foot between the alternator and the regulator-rectifier. Having said all of that, I am still fully confident that the wiring path that I chose will work sufficiently well.

16.6 Regulator-Rectifier Connections

As explained in “Replacing the Regulator-Rectifier for the 12-Volt Upgrade” on page 27, I replaced the Tympanium regulator-rectifier that John installed with a Podtronics regulator-rectifier. Because the Podtronics has the same installation footprint as the Tympanium (but is 1/4 inch thicker), I used the same two fixing bolts to secure the Podtronics to the back wall of the battery box.


Testing the 12-Volt Upgrade

I threaded the four wires of the Podtronics through a rubber-grommet-lined hole in the back of the battery box, and crimped an insulated male spade connector to each wire. Two of the wires are yellow and connect to the two AC terminals of the Podtronics. The third wire is black and connects to the negative (-) DC terminal of the Podtronics, and the fourth wire is red and connects to the positive (+) DC terminal of the Podtronics.

I then hand-held the battery box in place and plugged the four male spade connectors on the regulator-rectifier into the four female spade connectors at the end of the rectifier branch of the wiring harness:

yellow wire to green/yellow wireyellow wire to white/green wireblack wire to brown/white wirered wire to red wire

Because the yellow wires are for AC input to the Podtronics, either yellow wire can be connected to the green/yellow wire, and the other yellow wire can be connected to the white/green wire.

For the time being, I gently lowered the battery box (without battery) until it hung from the four plugged-in spade connections.

17.0 Testing the 12-Volt Upgrade

With all the electrical connections completed and the two fuses installed in their fuse holders, I was ready to test the 12-volt upgrade. I did the engine-off testing first.

I tested the 12-volt upgrade in three stages:• Testing with no battery or lamp bulbs installed

• Testing with battery and lamp bulbs installed

• Testing with battery and lamp bulbs installed and engine running

17.1 Testing with No Battery or Lamp Bulbs Installed

To prepare for this testing, I installed the PRS8 ignition/lighting switch in accordance to the following procedure:1. Hand-held the switch directly under the switch mounting hole in the nacelle top.

2. Oriented the switch to its mounting position: terminal 2 to the front of the nacelle and slightly toward the ammeter.

3. Pressed the switch through and up against the switch mounting hole.

4. Placed an alloy base plate (with a black-colored center and silver-colored “H,” “P,” and “O” letters) on top of the switch mounting hole and onto the ignition shaft of the switch.

5. Threaded the fixing nut onto the ignition shaft; placed masking tape around the fixing nut and on top of the base plate to protect the paint on the base plate; tightened the fixing nut with a wrench; and removed the tape.



6. Placed the switch knob onto the ignition shaft and secured the knob with the knob screw.

7. Inserted the ignition key through the ignition-key rubber grommet into the ignition shaft.

I then set up my digital multimeter to perform wiring resistance and continuity tests by selecting the ohms (“Ω”) function on the multimeter and pressing the RANGE button several times until “Ω” (not “KΩ” or “M Ω”) appeared in the display area.

I started by checking that no short to ground existed between the negative and positive terminal leads of the battery: I placed one multimeter probe on the battery’s negative terminal lead (ring connector of the brown/blue wire in the battery area), and the other multimeter probe on the battery’s positive terminal lead (ring connector of the red wire in the battery area). The resistance reading was OL (open loop, infinity). I was off to a good start!

Note: An open loop, or open circuit, has an infinite resistance. The electrical opposite of an open loop is a closed loop, or complete circuit, which has a finite resistance. A short run of just wires and closed switch contacts has virtually zero (0) ohms of resistance.

I then placed one probe on the battery’s positive terminal lead, and the other probe on the female spade connector of the brown/black ground wire to the horn, to check continuity between chassis ground and the horn’s ground terminal when the horn push switch is pressed. With the horn push switch not pressed (open), the resistance reading was OL; with the horn push switch pressed (closed), the resistance reading was 00.1 ohms. Great! So far, so good.

I then placed one probe on the battery’s negative terminal lead, and the other probe on various points, starting with the stop-lamp’s bulb contact, then the horn’s hot wire, and then the PRS8 switch output wires for the following switch positions:• Lighting switch set to “O”: all lights off.

• Lighting switch set to “P”: pilot (parking) lamp, speedometer lamp, and tail lamp on.

• Lighting switch set to “H”: headlamp, speedometer lamp, and tail lamp on.

• Ignition switch set to central position (between “IGN” and “EMG”): ignition off.

• Ignition switch set to “IGN”: ignition on.

Here are the resistance readings between the battery’s negative terminal lead and the:• Stop-lamp bulb’s contact when the rear brake pedal is not pressed (stop-lamp switch open):

OL.

• Stop-lamp bulb’s contact when the rear brake pedal is pressed (stop-lamp switch closed): 00.3 ohms.

• PRS8 lighting switch set to “O”:

Headlamp’s main beam contact when the dipper switch is set to main beam: OL.

Headlamp’s main beam contact when the dipper switch is set to dip beam: OL.

Headlamp’s dip beam contact when the dipper switch is set to dip beam: OL.

Headlamp’s dip beam contact when the dipper switch is set to main beam: OL.

Pilot-lamp’s bulb contact: OL.



Speedometer-lamp’s bulb contact: OL.

Tail-lamp’s bulb contact: OL.

• PRS8 lighting switch set to “P”:

Headlamp’s main beam contact when the dipper switch is set to main beam: OL.


Headlamp’s dip beam contact when the dipper switch is set to dip beam: OL.


Pilot-lamp’s bulb contact: sometimes 00.0 ohms, and sometimes OL. That is, when switching the lighting switch from “O” to “P,” I sometimes saw the expected 00.0 ohms, and I sometimes saw the unexpected OL. Hmmm . . ., not good . . .

Speedometer-lamp’s bulb contact: 00.0 ohms.

Tail-lamp’s bulb contact: 00.2 ohms

• PRS8 lighting switch set to “H”:

Headlamp’s main beam contact when the dipper switch is set to main beam: 00.1 ohms.


Headlamp’s dip beam contact when the dipper switch is set to dip beam: 00.1 ohms.


Pilot-lamp’s bulb contact: OL.

Speedometer-lamp’s bulb contact: 00.0 ohms.

Tail-lamp’s bulb contact: 00.2 ohms.

• PRS8 ignition switch set to central (off) position:

Regulator-rectifier’s female spade connector on brown/white wire: OL.

Transistor box’s pin connector on white wire: OL.

• PRS8 ignition switch set to “IGN”:

Regulator-rectifier’s female spade connector on brown/white wire: 00.0 ohms.

Transistor box’s pin connector on white wire: 00.0 ohms.

After troubleshooting to find out why the pilot-lamp’s bulb contact was sometimes OL when switching the PRS8 switch from “O” to “P,” I determined that the PRS8 switch could not consistently make a connection between its terminals 1 and 2 when switched from “O” to “P.” (Interestingly, when switching the PRS8 switch from “H” to “P,” the pilot-lamp’s bulb contact was always the expected 00.0 ohms.) My solution to the problem was to replace the PRS8 switch with another new (rebuilt) PRS8 switch. The difference between the first and second PRS8 switch installations was that for the second installation, I used my multimeter to verify that the switch was switching properly before I installed the switch.



17.2 Testing with Battery and Lamp Bulbs Installed

To prepare for this testing, I installed the battery box, the battery (fully charged), the headlamp bulb, the pilot-lamp bulb, the speedometer-lamp bulb, and the stop-tail-lamp bulb in accordance to the following procedure:1. After ensuring that no wires would be trapped behind the battery box during the fitting,

fitted the battery box to the central upright frame tube. Tightened two fixing bolts to secure the battery box to two frame brackets (tabs).

2. Placed a rubber pad in the battery box and set the right side of the lithium-iron 12-volt battery on the rubber pad, with the battery’s front facing left (positive terminal above the negative) so as to maintain a comfortable distance between the battery’s terminals and the front battery retaining strap; surrounded the battery with foam strips to cushion the battery and to ensure that it would not move around in the battery box; tightened the bolt in the top battery retaining strap to the front battery retaining strap; and connected the brown/blue lead to the battery’s negative terminal and the red lead to the battery’s positive terminal.

Note: Both fuses, the one in the brown/blue lead to the battery’s negative terminal and the one in the brown/white wire to the regulator-rectifier’s negative terminal, are easily accessible through the battery box. I plan on carrying extra fuses in the battery box, and will stash a flat-blade screwdriver somewhere on my bike to access the fuses by removing the slotted screw from the front cover of the battery box.

3. Placed a headlamp double-filament pre-focus bulb in the bulb flange of the headlight unit; engaged the three projections in the headlamp bulb holder with the corresponding slots in the bulb flange; and pressed the bulb holder inward and turned it clockwise to lock it into place. I then gently lowered the headlight unit until it hung from the headlamp bulb holder.

4. Fitted a pilot-lamp bulb into the pilot-lamp bulb holder by pressing the bulb inward and turning it clockwise; then push-fitted the bulb holder into its housing on the reflector of the headlight unit.

5. Fitted a speedometer-lamp bulb into the speedometer-lamp bulb holder by pressing the bulb inward and turning it clockwise; then push-fitted the bulb holder into its housing on the speedometer.

6. Fitted a stop-tail-lamp double-filament bulb into the stop-tail-lamp bulb holder by (1) engaging the two offset pins on the bulb with the corresponding slots in the bulb holder and (2) pressing the bulb inward and turning it clockwise; then replaced the stop-tail-lamp lens and tightened the two slotted sleeve nuts.

I then used my digital multimeter to check my battery voltage. (Because I had used my Battery Tender Junior 12V battery charger to charge the battery the night before, I was confident that the battery voltage would be at a high level.) I selected the VDC function on the multimeter; pressed the RANGE button several times until “v” (not “mv”) appeared in the display area; and placed the black probe on the battery’s negative terminal and the red probe on the battery’s positive terminal. The voltage was 13.2 Vdc, which was higher than the acceptable range of 12.3 to 12.6 Vdc.

Note: Possibly the acceptable range of 12.3 to 12.6 Vdc applies to a properly charged lead-acid battery rather than a properly charged lithium-iron battery? Not sure.



I checked the pilot lamp, speedometer lamp, and tail lamp by setting the PRS8 lighting switch to “P”; then checked the headlamp (both main and dip beams), speedometer lamp, and tail lamp by setting the PRS8 lighting switch to “H”; and then checked the stop lamp by pressing the rear brake pedal. All lights worked as expected. The ammeter showed a steady discharge of about four amps (needle moved to the left) when the headlamp was turned on.

I checked the horn by pressing the horn push switch. The 3-amp horn sounded really nice and loud!

And finally, I checked the ignition by removing the spark plugs and, with the spark plugs connected and lying on top of the cylinder head fin, set the PRS8 ignition switch to “IGN,” pressed the kickstarter to roll over the engine, and checked for spark. Voila! I had spark!

17.3 Testing with Battery and Lamp Bulbs Installed and Engine Running

To prepare for this testing, I installed the fuel tank, the twinseat, the nacelle top, the headlamp fixing ring, and the headlight unit (with rim attached) in accordance to the following procedure:1. Removed the fuse in the brown/blue lead to the battery’s negative terminal.

2. After fitting a rubber pad to each of the four tank-mounting brackets (tabs) on the frame, fitted the fuel tank on top of the four rubber pads and used four fixing bolts, four washers, and four more rubber pads to secure the fuel tank to the frame; locked the four bolts by re-threading the two locking wires through the heads of the two rear bolts and the heads of the two front bolts; connected the fuel pipes to the Amal carburetor; and added more fuel to the tank.

Note: The previous owner of my 1955 Triumph 6T replaced the factory-original SU MC2 carburetor with an Amal Monobloc carburetor.

3. Fitted the twinseat in position; replaced and tightened the front fixing bolt; and tightened the two rear fixing bolts that were loosened during the removal of the twinseat.

4. Holding the headlight unit in my hand, pressed the headlamp bulb holder inward and turned it counterclockwise to unlock it from the headlight unit; pulled the pilot-lamp bulb holder from its housing on the reflector of the headlight unit; and set the headlight unit aside.

5. Fitted the nacelle top onto the left and right nacelle-handlebar rubber grommets and onto the left and right nacelle covers; replaced and tightened the two screws and two nuts that secure the rear of the nacelle top to the nacelle covers; replaced and tightened the four screws and two nuts that secure the left and right motifs and the sides of the nacelle top to the nacelle covers.

6. Connected the speedometer drive cable to the speedometer.

7. Fitted the headlamp fixing ring onto the nacelle headlamp body, and replaced and tightened the two screws that secure the fixing ring to the nacelle headlamp body.

8. Holding the headlight unit in my hand, engaged the three projections in the headlamp bulb holder with the corresponding slots in the headlight unit’s bulb flange, pressed the bulb holder inward and turned it clockwise to lock it into place; and push-fitted the pilot-lamp bulb holder into its housing on the reflector of the headlight unit.



9. Fitted the headlight unit onto the headlamp fixing ring (by first engaging the bottom edge of the rim with the underside of the fixing ring) and tightened the rim retaining screw and securing plate at the top of the fixing ring.

10. Checked the main beam setting by placing my bike on a level surface in front of a light-colored wall at a distance of about 25 feet (eight meters); sat on the twinseat because the weight of the rider affects the setting; and set the PRS8 lighting switch to “H” and the dipper switch to the main beam.

Because the main beam was directed a little low and thus not parallel with the ground, I loosened the two screws on the headlamp fixing ring and raised the beam by pulling out the bottom of the fixing ring. When the main beam was directed straight ahead, I retightened the two screws.

Note: With the Lucas pre-focus type bulb fitted in the headlight unit, the filament is correctly positioned during manufacture in relation to the focal point of the reflector in the headlight unit. No further focusing is necessary.

11. Replaced the fuse in the brown/blue lead to the battery’s negative terminal.

Then, after (1) engaging the gearbox in the neutral position, (2) turning on the right-hand (main-supply) fuel tap, (3) pulling in the clutch lever and operating the kickstarter two or three times to separate the clutch plates, (4) closing the Amal carburetor choke valve by turning the choke lever on the left-hand back-stay frame tube immediately under the twinseat fully counterclockwise, (5) depressing the Amal carburetor tickler three times to flood the carburetor, (6) setting the PRS8 ignition switch to “IGN,” and (7) turning the throttle twistgrip 1/8th of a turn, I kick-started the engine and verified that all lights were still working. I also observed a steady charge on the ammeter (needle moved to the right) as I opened the throttle twistgrip to increase the speed of the engine.

Note: After the engine started, I opened the carburetor choke valve by turning the choke lever fully clockwise.

With my wife throttling the engine to about 3500 revolutions per minute, I checked the battery charging voltage with the lights off; the voltage was 14.0 Vdc. Then, I checked the battery charging voltage again with the lights on; the voltage dropped to 13.8 Vdc. Both voltages were within an acceptable range, and were higher than the basic battery voltage of 13.2 Vdc. I then pressed the front cover onto the battery box and secured it with the slotted screw.

Then, during the day, I went for a test ride. At cruising speed with the lights off, the ammeter showed a steady charge, meaning that current was going into the battery. Only a couple of amperes of current were going into the battery because my battery was fully charged. At low speed with the headlamp on, the ammeter showed a steady discharge, but as I increased the engine speed, the discharge lessened, and at cruising speed, the ammeter needle was slightly right of center.

The battery voltage readings and the ammeter current readings all indicated that my charging system was able to cope with the electrical load! Good news, indeed.


Farewell Comments and Suggestions for the 12-Volt Upgrade

18.0 Farewell Comments and Suggestions for the 12-Volt Upgrade

Not to blow my own horn, but I must say that the installed (modified) main wiring harness really looks professional! Having said that, if I had to do the whole thing all over again, I would probably buy the properly color-coded wires from British Wiring and build my own wiring harness.

I purchased online a machining service that replaced the crankshaft bush in my timing cover with an oil seal, a modification that presumably increases oil pressure. The machining service replaces the bronze bush in a pre-unit Triumph twin timing cover with a standard oil seal and circlip, like the standard oil seal and circlip in a Triumph unit-construction timing cover. Although the bush-to-oil-seal modification is controversial (some pre-unit Triumph twin experts say that the stock oil pump is more than capable of dealing with the oil pressure loss due to a worn bush), I decided to go ahead with the modification.

As a preliminary step to repainting my fuel tank, which sat in a garage with the rest of my bike for 21 years, I coated the inside of my tank with an epoxy sealer to eliminate any possibility of a leaky tank ruining the new paint job. As of today (knock on wood), the new paint job is holding up well! If you have a vintage motorcycle that hasn’t been ridden for a long time, consider lining your fuel tank with an epoxy sealer before repainting your tank. Online instructions for doing so are given in “Apply an Epoxy Sealer on a Leaking Gas Tank” at http://www.motorcycleclassics.com/mc-how-to/apply-epoxy-sealer-leaking-gas-tank.aspx.

That’s about it for the restoration and 12-volt upgrade of my 1955 Triumph 6T motorcycle. The restoration unveiled a classic motorcycle that looks better than new. The upgrade added the convenience and safety of a modern 12-volt charging and ignition system without changing the unbeatable look of a classic motorcycle.

I just finished cleaning and polishing my bike to a high shine. It looks like a show bike! Now, if I can just convince my “old lady” (wife) to climb on the back of my bike and take a ride with me . . .

19.0 Wiring Diagrams for the 1955 Triumph 6T and the 12-Volt Upgrade

Figure 1 through Figure 9 pertain to the original wiring of the 1955 Triumph 6T and the 6-volt system. Figure 10 and Figure 11 pertain to the wiring of the 12-volt upgrade for my 1955 Triumph 6T.


http://www.motorcycleclassics.com/mc-how-to/apply-epoxy-sealer-leaking-gas-tank.aspx

Wiring Diagrams for the 1955 Triumph 6T and the 12-Volt Upgrade

Figure 1 Wiring Diagram for 1955 Triumph 6T (Ignition Off, Lighting Off)

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Figure 2 Wiring Diagram for 1955 Triumph 6T (Ignition Off, Pilot Lighting On)

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