gathering of the green 2008 winter conventionjd2cylservice.com/gog2008.pdf1 gathering of the green...

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Gathering of the Green2008 Winter Convention

March 12 - 15Moline, IL

Carburetors: History, Application and ServicingWheeler Schebler D

Marvel Schebler TCX, TSXDLTX 1 barrelDLTX 2 barrel

Duane LarsonKnoxville, TN

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Introduction

• Carburetors require periodic servicing and repair to properly perform their function– Provide the proper mixture of fuel and air, in

the proper amount, to the engine• Workshop has been led by Bob Beaver of

Roberts Carburetor Repair– Now RETIRED

• I have researched and rebuilt carburetors and magnetos for over 25 years– Got “volunteered” to lead this workshop

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Acknowledgements and References

• Several folks have answered my call for information– Bob Beaver– Steve Ridenour and Jack Kreeger – Y, 62– Kent Pribil – Spoker D (leading workshop)– J. R. Hobbs – Nice books on Unstyled and Styled

Deere tractors• References

– Carburetor manuals– Deere parts books and SM-2024 Carb Manual– Carburetors and Carburetion – Walter Larew– Field Service Bulletins

• Handout available – Application ChartHandouts from the Gathering of the Green workshops are among the information included on the CD available through this web site.

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Outline of Talk

• History of the carburetor companies – Wheeler-Schebler, Marvel, Ensign, Zenith

• Identify the various types of carburetors– Air valve, plain tube, updraft..

• How carburetors work– Study systems which make up a carb

• Fuel, idle, load, acceleration, economizer..

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Outline of Talk

• Discussion of particular carburetors– Schebler D series used on Waterloo Boy, D– Marvel Schebler

• DLT 1 barrel• DLT duplex (2 barrel)• TSX

– Ensign• Covered by Cork Groth in his Workshop

• Repair suggestions with each series

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Deere Carburetor History

• Carburetors all follow from Wheeler-Schebler and Marvel linage– Two exceptions

• Ensign Bj and Kj series used on GP, few D’s• Zenith TU series used on diesel starting engines

• George Schebler and Burt Pierce– Fiddle makers/woodworkers in Indianapolis– Developed two carburetor styles– Flipped coin

• Schebler pursued Air-valve design– Patent 1902

• Pierce pursued “Marvel” design– Patent 1909

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• Frank Wheeler funded Schebler design– Formed Wheeler-Schebler ~1905 (1901?)– Built new facilities 1911– Wheeler bought out Schebler in 1914 for $1m

• Sugar futures in WWI – both lost fortunes– Wheeler died May 1921– Schebler died November 1942

• Wheeler-Schebler very successful– Carburetors used on all Waterloo Boys and Ds– Factory still standing – Wheeler Arts Center

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Wheeler-Schebler Model D Carburetor

Gas Review September 1917

Gas Review November 1913

Used on tractors, boats, and stationary engines, including the Waterloo Boy and Model D tractors

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• Marvel Carburetor Company formed 1908– J. R. Francis funded Burt Pierce’s Marvel design– Sales to the new General Motors increased

• Marvel moved to Flint MI in 1912• Pierce sold interests, became consultant

– Developed carburetor cleaner - Marvel Mystery Oil

– 6000 carburetors/day produced in 1928• Marvel bought Wheeler-Schebler March 1928

– Wheeler Schebler operations moved to Flint July 1931• Borg-Warner company formed June 1928

– Four companies, including Marvel• Designated Marvel-Schebler Division in 1934

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• Marvel Schebler moved to Decatur, IL 1948– Opened new factory October 1950

• Borg Warner sold Marvel Schebler carburetor line to Facet Enterprises in 1982– Decatur plant closed April 15, 1983

• Facet sold Marvel Schebler product line to Zenith Fuel Systems 1990

• Comment on Schebler model identification– Start with Schebler D series

• Evolved to Schebler DL (DeLuxe) plain tube motorcycle series– Evolved to DLT (Tractor) plain tube series for Deere

– DLTX used by Deere, where X is part of the part number

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• Ensign Carburetor Company– Formed in 1911 by Orville H. Ensign

• Huntington Park, CA (near Los Angeles)• First carburetor based on 1912 patents

– Tractor customers included• IHC• Holt and Caterpillar• Hart Parr/Oliver• John Deere

– Transitioned to LP-Butane carburetors in ’40’s– Sold to American Bosch 1960– Hard to find carburetor parts or literature

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• Zenith Carburetor– Based on French design of M. Baverey– Licensed to Zenith-Detroit Corporation

• Began building carburetors in 1909• Purchased by Bendix Aviation February 1935

– Vincent Bendix invented the Bendix starter

– 1930’s sold carburetors to most tractor builders– R20TP line used on both Novo and Hercules

engines in Model Y Wagon Works tractor– TU line used on diesel starting engines– Company in business as Zenith Fuel Systems

• Provide some Marvel Schebler parts

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Carburetor Types

• Different basic designs used by Deere– Air Valve carburetor

• Wheeler Schebler D– Used on Waterloo Boy and early D’s

• Has no venturi• Air valve and spring operation critical

– Plain Tube carburetor• Also called Natural Draft, Single- or Dual-Induction, or

Straight Through carburetors• Schebler DLT series

– Waterloo letter and number series tractors

• Uses a venturi

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Carburetor Types

– Updraft carburetor• Schebler TCX, TSX series

– L, LA series, Dubuque series tractors

– Downdraft carburetor• Zenith TU series

– Diesel Starting Engines

– Mixing Valve (too simple to be called a carb)• Marvel Schebler SL-2

– R diesel starting engine

– LP carburetors• Schebler TSG series for Dubuque series• Deere carburetors using MS parts for Waterloo

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Principles Applicable to all Carburetors

• A carburetor must do two things– Control amount of fuel/air mixture to cylinders

• Position of the throttle plate– Control the ratio of fuel to air in the mixture

• Opening of load and idle needles• Vapor mixture about 2% fuel, 98% air• Nebraska Test 222 1934 A Rated Load test

– Used 5.6 gal air and 0.5 teaspoon fuel in one second» Equivalent to 0.11 gal fuel vapor

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How Carburetors Work

Calvin and Hobbes by Bill Watterson

Well, lets see if we can figure it out……

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• It’s all due to Air Pressure (or lack thereof)• Close to sea level pressure is 14.7 psi

– Air has weight – 88 lbs in a 12x12x8 ft room• “Vacuum” is a pressure less than 14.7 psi

– Often measured in inches of mercury• 14.7 psi ~ 30 in Hg

• As engine runs, intake strokes create “vacuum” or lower air pressure in manifold– Normal ~10 psi (~20 in Hg)

• With throttle plate open, carburetor throat exposed to manifold pressure

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• Carburetors operate on the venturi effect• The venturi is a narrowing of the bore

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• What causes air flow through carburetor?– Intake stroke of piston creates vacuum

• Intake valve open, transmits vacuum to throttle plate

– Position of throttle plate determines air flow• Closed – no flow – high manifold vacuum• Open – full flow – low manifold vacuum

– Air (at ~ atmospheric pressure) flows from air cleaner side, through venturi, past throttle plate, through manifold and intake valve, into cylinder

• Model A running at 975 rpm flows about 70 cfm

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• As air flows through venturi, pressure decreases in venturi– Bernoulli’s Law tells us as Area decreases, velocity

increases• and

– As velocity increases, pressure decreases• Air pressure on fuel in bowl is always ~atmospheric• As pressure difference between 1) fuel in bowl and

2) at tip of nozzle (located in venturi) increases, fuel flow increases from nozzle– Throttle opens, more air flow, greater ∆P, more fuel flow– Throttle closes, less air flow, less ∆P, less fuel flow

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• Important factors– Amount of vacuum created by intake stroke

• Less vacuum if– Intake valve guides leak air– Exhaust valve leaks air– Piston rings leak air– Manifold gasket leaks air

– Position of throttle plate• Determines air flow through carburetor

– Determines difference in pressure on fuel in bowl and at tip of nozzle in venturi

» Greater difference – more fuel flow

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How Carburetors Work – Throttle system

θ

% Bore open = πb²(1 - cosθ)x100

“Bore Open” is difference between bore size and area of throttle plate

b = radius of bore size

θ % Bore Open 0 0.0 10 1.5 14 3.0 17 4.4 24 8.6 30 13.4 33 16.1 41 25.0 45 29.3 60 50.0 75 75.0 84 90.0 90 100

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• Venturi region– Bernoulli’s Law tells us as

Area decreases, velocity increases

– and– As velocity increases,

pressure decreases

• Incoming air 14.7 psi• Venturi pressure 8 psi• Outgoing air ~10 psi• Pressure difference

14.7 – 8 = 6.7 psi• So fuel flows out of venturi

into the air stream to the manifold and cylinders

Venturi

To manifold

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How Carburetors Work – Necessary systems

• Previous carburetor fine for fixed speed hit ‘n miss engine

• Refinements needed for tractor carburetor– Fuel supply system

• Means of maintaining correct fuel level in bowl– Choke system

• Means of regulating amount of air for starting– Throttle system

• Means of regulating amount of fuel-air mixture– Idle system

• Means of supplying just enough fuel-air mixture to run with no load

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How Carburetors Work – Necessary systems

– Load system• Means of metering correct fuel-air ratio above idle

– Accelerating system• Provide adequate fuel when throttle opens quickly

– Economizer system• Retards fuel flow at part throttle speeds• Solves common carburetor design problem

• Look at these seven systems on a Marvel Schebler DLT series one barrel carburetor– Simple example and a popular carburetor

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How Carburetors Work – fuel supply system

• Fuel flows through a strainer to the needle and seat, then to the fuel bowl

• Seats are brass, needles have steel tips (vitonavailable)

• Fuel level – measure with 1/8”NPT fitting in bowl drain hole, and clear plastic tubing– All DLTX except 67-73

• 3/4” down from bowl gasket– DLTX67-73

• 5/8” down from bowl gasket• Bowl baffles allow higher level

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How Carburetors Work – Choke system

• Used for starting and warm-up

• Manifold is cold– Only volatile parts of fuel

vaporize– Need more fuel

• Choke restricts air flow– Further reduces venturi

pressure• Produces more fuel flow

• Slot on choke lever always parallel to plate

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Choke Plate Locating Line on Choke Lever

Line always parallel to choke plate position

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How Carburetors Work – Choke system

• Waterloo Boy’s did not have choke system• Not functional for starting on D’s built before

109944 (Nov 1, 1930)• Spring-loaded choke lever and choke plate in

place, but…..– Had no mechanism in place to operate during starting– Instruction manuals make no reference to use– Starting instructions are to use 1 tablespoon High Test

gasoline in each petcock– Would have to use wire to hold open – none furnished– Useful after starts to choke by hand until warms up

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How Carburetors Work – Throttle system

• Throttle plate – Regulates amount of fuel-

air mixture entering engine

– Regulates amount of fuel in mixture

– Varies engine speed• Governor connected to

throttle plate and speed control lever– Governor maintains rpm– Increase load, governor

opens throttle plate to maintain rpm

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How Carburetors Work – Idling System

• Slow idle – throttle shut• Provide fuel-air to keep

engine running– Primary idle hole sees manifold

vacuum– Air enters, picks up fuel at idle

needle, mixture goes out primary hole

• Air enters secondary hole

• Fast idle – both holes open –richer mixture

• Good system – works under high suction, mixture flows at high velocities in small passages

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DLT Idle Circuit Passages

Idle Circuit

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How Carburetors Work – Idling System Problems

• Unmetered air– Worn shaft bushings– Bushings not fitted to

throttle plate– Brass plug threads– Idle needle threads

• Plugged passages– Air entry into idle needle– Small passage at

bottom of idle needle– Primary and secondary

holes– Remove all brass plugs,

ream to size

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How Carburetors Work – Accelerating System

• At idle, no venturi flow• Fuel rises in nozzle by load

needle to level in fuel bowl• Holes in nozzle let fuel flow

into cavity around nozzle– “accelerating well”

• Open throttle rapidly– Venturi effect

• Fuel flows thru nozzle• Also from accelerating well

thru holes in nozzle

• Accelerating well provides necessary extra fuel for richer fuel-air mixture

• Holes serve as air bleeds

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How Carburetors Work – Load System

• As throttle plate opens manifold vacuum causes air flow across nozzle in venturi– Creates pressure difference

between fuel in bowl and nozzle tip

– Atomized fuel flows out of nozzle, mixes with air

• Amount of fuel controlled by load needle– Close too far, engine misses– Open too far, fuel rises, extra

flows out holes in nozzle, black smoke

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How Carburetors Work – Economizer System

• Carb design problem– Too rich at part throttle

• Load system operating– Lean out mixture

• Air enters passage with outlets to fuel bowl and near throttle plate– Hole near plate holds

economizer plug

• Throttle plate exposes hole to vacuum, reduces pressure on fuel bowl– Reduces fuel flow from

nozzle

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Air Intake Passages – DLT Carburetors

Idle Air Intake

Bowl Vent Air Intake

Accelerating Well Air Intake

Looking in Choke End of DLTX51

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How Carburetors Work – Starting Engine

• Starting a tractor– Open gas supply to carburetor

• Fuel flows into bowl, past load needle into nozzle, and thru nozzle holes into accelerating well

– Close choke– Advance throttle lever half way (Owner’s Manual)

• Fully open throttle plate• Closed choke plate

– Full manifold vacuum applied to nozzle tip

– Turn flywheel to create manifold vacuum• Difference between pressure on fuel in bowl and nozzle tip

causes fuel to flow from nozzle and acceleration well

– Tractor starts– FSB 200 recommends nearly closed throttle plate

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How Carburetors Work - Idling

• Slow idle (throttle lever pulled back)– Throttle plate nearly closed

• Only primary idle hole open to manifold vacuum• Secondary hole adding air

• Fast idle (throttle lever wide open)– Throttle plate open to expose both primary and

secondary idle holes to manifold vacuum– Fuel flows from both idle holes

• Maximum flow of fuel in idle circuit

• Amount of fuel allowed into idle circuit controlled by idle needle

• Insufficient air flow past throttle plate for venturi action

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How Carburetors Work - Idling

• Setting idle needle for slow idle– Pull throttle lever back to slow idle stop

• DLTX67-73 carbs, engine will stop– Throttle plate hides both idle holes from manifold vacuum– Do not pull lever back to stop to set idle

– Want only primary idle hole exposed to vacuum• Air for idle circuit enters at venturi on right side• Fuel enters at idle needle seat to create fuel-air mixture

– Idle circuit MUST be clean and to size• Fuel-air mixture exits primary hole to manifold vacuum

– Secondary hole provides additional air– Start with idle needle open ~1 turn, open 1 notch…..

• Wait for 15 sec, open, … repeat• No unmetered sources of air

– If settings don’t work for middle or fast idle, check idle hole sizes

– Lean a setting as possible to reduce plug fouling

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How Carburetors Work – Sudden Load Applied

• Carburetor goes from idle to load circuits– At idle, acceleration well full– When load suddenly applied, extra fuel needed

• Governor opens throttle plate quickly– Full manifold vacuum applied

• Venturi action starts pushing fuel from bowl thru nozzle• Additional fuel flows through nozzle holes

– Provides rich mixture for short time until well empties

– If load remains• Nozzle holes act as air bleeds, air comes from well vent• Provides proper fuel-air mixture for load

– If load goes away• Back to idle circuit operation, accelerating well refills

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How Carburetors Work – Under Load

• Throttle plate opening set by throttle lever and governor

• Manifold vacuum and venturi effect causes fuel to flow from nozzle– Amount depends on desired engine speed

• If lever set mid-range, economizer circuit leans out the fuel-air mixture

• If lever set wide open, throttle plate open past economizer plug opening, venturi action overcomes economizer action, increases fuel in mixture

• If lever wide open and rated load applied, throttle plate wide open, venturi action and fuel-air ratio maximized

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How Carburetors Work – Under Load

• Setting load needle – done under load– Apply rated load to engine– Close load needle until engine sputters

• Fuel flow thru needle less than flow thru nozzle– When fuel level drops below nozzle bottom, draws air

– Open load needle until black smoke• Fuel flow thru needle greater than flow thru nozzle

– Fuel flows up into acceleration well and out nozzle holes» Fuel-air mixture too rich for engine to burn

– Set load needle ~ half-way between close and open positions

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Discussion of particular carburetors

• Early Wheeler Schebler carburetors on Waterloo Boy and D

• DLTX1• DLTX3• Brass and cast iron carburetors• General DLT series carburetors• DLTX67-73• Universal DLT replacement carburetors

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Wheeler Schebler Model D Carburetor

Choke unit

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• Original Schebler design – sold since 1904• Air-valve design

– No venturiAir Valve

Nozzle

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• Carburetor not very sophisticated– No idle circuit– No venturi– Has bowl vent– Setting of air valve seems important

• Operation– As throttle plate opens, manifold vacuum is applied,

action similar to having choke on– Atmospheric pressure acts on fuel in bowl– Low pressure across nozzle tip causes fuel to flow,

needle valve sets amount of fuel• Loosen air valve – more air allowed in, less pressure

difference – less fuel – engine slows down• Turn air valve in – spring holds valve tighter – less air in,

more pressure difference, more fuel, engine speeds up

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• Combination of needle valve setting and air valve spring tension very important

• Air valve setting normally 1/2” to 5/8” from body

• Condition of spring important for correct pressure on valve

• There are good-running Waterloo Boys and spoker D’s, so apparently it can be done…

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Early Wheeler Schebler Carburetors

• Waterloo Boy used Schebler D– No choke device listed in parts books– No throttle shaft bushings

• Model D also used Schebler D– AD-28

• 30401-30450• Different part numbers than DX298 or DX304

– AD-107 • 30451 – 31304

– DX298 (used in Nebraska Test 102 on 30504)

• 31305 - 49773– DX304

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Wheeler Schebler DLTX1

• Used on 605 D’s between 39907 and 46767– AD107 DX304 Schebler D was “usual” carburetor– AD287 DLTX1 was “trial”

• Air intake end has no flange– AD411 DLTX3 followed DX304, started at 49774

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Wheeler Schebler DLTX3

• Model D from 49774 – 109943 (mid ’27 – ’30)– Replaced by DLTX6 at 109944 (Nov 1930)

• Linkert brass float (H-D motorcycle) works• Bowl vent not in air passage• Most parts available• Only 1 idle hole outlet

Bowl Vent hole

(Load Needle)

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Brass vs Cast Iron Carburetor Bodies

• Brass (actually bronze) carburetors were used on the A, AR series, D, and GP series

• DLTXa (brass) went to DLTXa+10 (cast iron)• First B Oct-2-34 used cast iron carb• Change from brass to cast iron

– A – early December 1935 DLTX8 to DLTX18– AR-AO-AI – mid April 1936 DLTX9 to DLTX19– D – late April 1936 DLTX6 to DLTX16– GP is confusing (as usual!!)

• Appears all Schebler carburetors were brass from the factory

– DLTX5 for GP, GPO, GPWT, and DLTX7 for OTS GPWT

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General DLT series carburetors

• All same size, so will interchange physically– Terrible idea, though!

• Don’t swap D carb with carb for other model– Governor rod on opposite side of pivot

• Governor tries to slow down – but speeds up.. baad

• Some parts critical to operation are different– Nozzles– Throttle and choke plates– Economizer plugs– Internal passage sizes

• Primary and secondary idle holes

• Make sure all internal passages are clean

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General DLT Series Carburetor Issues

• Eliminate sources of unmetered air– Fit bushings to interior shape– Seal threads on brass plugs and needles– Make flanges flat (machine or sand)

• Set float for proper fuel level– Use hose barb and clear tubing in bowl drain– 3/4” down from bowl gasket for all carbs with

metal floats, EXCEPT– 5/8” for DLTX67-73 carbs

• Clean strainer under screen – rusty• Use pliable gaskets, not hard ones

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General DLT Series Carburetor Issues

• Check surface where seat sets– Often pitted – resurface smooth

• DLTX67-73 (late A and B)– Two brass bowl vent plugs in vent hole

• Make it hard to tell if vent hole is open– If plugged, cause all sorts of problems

• Carb operation depends heavily on correct pressure on fuel in bowl

– Spring-loaded off-center choke• Partially opens when tractor starts

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Duplex Carburetors

• Operation• Service hints• Similar to single barrel carburetors

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Duplex Fuel Control System

• Fuel enters inlet, into sump– Traps dirt, drain to clean

• When sump full, flows through screen, needle, seat

• Proper fuel level at top of bowl/gasket

• Holding carb upside down, “top” of float should be 3/4” from bowl gasket surface

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Duplex Bowl Air Vent System

• Large Pitot tubes and passage vent fuel in bowl to atmosphere

• Blockage unlikely– Better than 1 barrel

• Pitot tubes also play role in choke and economizer systems

• All air passes through air filtering system

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Duplex Idle System – Slow Idle – 1 barrel

• 2 or 3 idle holes (2 in 1bbl)– When throttle closed

• One on manifold side• 1-2 on venturi side

• Manifold vacuum on 1st

Hole pulls air from Air Bleed hole and fuel from bottom of neck

• 2nd and 3rd idle holes add more air to lean out

• Idle needle controls mixture, not fuel alone

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Duplex Carburetor Idle and Load Fuel Feeds

Idle fuel feed holes

Load jets (removed)

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Duplex Idle Air Feeds and Nozzle Well Vents

Idle Air Feed Nozzle Well Vent

Holes toward center are Nozzle Well Vent holes

Holes toward outside are Idle Air Feed holes

Pitot Tubes

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Duplex Idle System – Fast Idle – 1 barrel

• 2nd and (then 3rd) idle holes exposed to manifold vacuum as throttle plate opens– Feed air-fuel mixture– Graduated system for

smooth operation• Merges into load

operation smoothly as throttle plate opens and venturi actions begins

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Duplex Accelerating System• During idle, no nozzle flow,

accelerating well fills to fuel level in bowl

• When throttle plate opened fast, lots of fuel needed– Full venturi vacuum so

maximum ∆P between nozzle top and bowl fuel

– In addition, fuel flows from accelerating well thru nozzle holes

• Engine speed increases, air flows from air bleed hole through nozzle holes to lean mixture out at steady state speed

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Duplex Load System

• Engine speed set by governor/speed lever

• Increase load, throttle plate opens, more ∆P, more fuel from nozzle

• Fixed load jets – Sized to carb and fuel– Limit fuel flow

• Metering screw– Center of bowl nut– Adds additional fuel– 2 ¼ turns open– Lots of service issues

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Duplex Economizer System

• Simpler than 1 barrel system– No economizer plug near throttle plate

• Carburetor designed for proper mixture at light load operation– Too lean for full load– Additional fuel must be supplied

• As throttle plates open under load– More air drawn, moves faster to manifold vacuum– Part of air “rammed” thru Pitot tubes, adding pressure

to fuel in bowl• Increased ∆P, more fuel flows as more air flows

• Decrease load, less air flow, less “ramming”

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Duplex Choke System

• Similar to 1 barrel carb• Choke disks close air flow

thru barrels– Flow thru Pitot tubes not

affected

• Maximum manifold vacuum on nozzle tops

• 14 psi pressure on fuel in bowl thru Pitot tubes– Max ∆P, lots of fuel flow from

nozzle and idle holes• Not much air flow

• Choke plates spring-loaded and offset– Engine starts, air flow pushes

disks open

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Duplex Repair Information

• Remove metering screw from center of bowl nut– Unscrew until loose, may have to pull– Inspect end – should have tapered ss piece held on

by small spring washer– Inspect metering screw seat

• Has slots for fuel flow, NOT unscrewing• No reason to remove

• Remove bowl, inspect– Often bent, bottom bowed in

• Press straight• Reproductions available

• Disassemble carburetor– Remove nozzles, throttle and choke plates, etc.

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Duplex Fuel Metering Screw

Spring Washer

New

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• Remove load jets• Remove idle needles• Identify holes where fuel enters idle circuit• Remove small freeze plugs just above bowl on

each side of carb– Carefully drill, tap for 10-32 screw, pull

• Can reuse, filling holes with JBWeld, or use new plugs

– See two holes– Good intermediate place to access idle circuit– Spray carb cleaner into idle pickup hole in neck

• Should come out hole

– Spray cleaner into hole toward idle needle• Should come out idle holes

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Duplex Carburetor Freeze Plug Removed

To Idle holes near throttle plate

From Idle Air Inlet

From Idle Fuel Inlet below nozzleIdle Needle (removed)

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• If carb cleaner does not come thru holes have blocked passages– Probably need to remove ball bearings

• Not brass plugs like in 1 bbl• Hard – Rockwell Hardness Rc48 at least

– Wire weld tail on ball, pull with slide hammer• May have to drill hole to top of ball to access

• Clean passages (once open)– Replace balls (or drill and tap for brass plugs)

• Clean nozzles• Inspect throttle shaft, bushings for wear

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• Check float– Place in boiling water, look for bubbles

• If see bubbles, bad float

• Check needle and seat– Pull vacuum see if hold

• Clean body, do any necessary repairs• Reassemble, set float level 3/4” • Use new, soft gaskets

– Bowl gasket goes under bowl, not under bowl nut• Can use hard gasket under nut

• Leak check, check fuel level (at bowl gasket)

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Marvel Schebler Universal Carburetors

• Between 1969 and 1974 all single and duplex carburetors were collapsed into three units

• DLTX107U replaced DLTX5, 8, 10, 15, 17, 18, 19, 26, 34, 46, 67, 73

• DLTX108U replaced DLTX3, 6, 16, 24, 33, 41, 51, 53, 63, 71, 72

• DLTX109U replaced all duplex units• Identified by circular aluminum tab with number

stamped on it, brass drill plugs riveted in, not threaded.

• Discontinued in 1983 when M-S plant closed

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TSX Series Carburetors

• Theory• Repair• Used on Wagon Works and Dubuque

series tractors– L, LA, LI, M, etc.– 62 and Unstyled L used TCX series (similar)

• Problem– Parts books list bowl separately but top

includes throttle shaft and plate• Hard to compare to see if tops can interchange

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TSX Basic Principles – Updraft Carburetor

• Similar concept to DLT• Air enters, passes thru

venturi where its velocity increases and pressure decreases, then back to low velocity and pressure

• Nozzle tip located in venturi at point of low pressure so fuel flows out nozzle

• Bowl vent connects to air inlet, as on DLT

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TSX Fuel and Choke Systems

• Fuel enters thru strainer– Fastened on end of inlet

• Flows thru needle and seat– Fuel level 5/8” below bowl

gasket

• Close choke to start– Extends manifold vacuum

past nozzle– Bowl vent takes air from left

side of choke• Large ∆P between nozzle tip

and fuel in bowl– Rich fuel-air mixture

• Engine starts – choke off center or has flap so air enters

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TSX Load System

• Some carbs have load needle, some have fixed load jet only

• Throttle plate position set by governor/speed control lever– Governor maintains speed

• More load, throttle opens more

• When maximum load applied, throttle plate fully open, maximum fuel-air mixture flows to engine

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TSX Accelerating System

• At idle, fuel flows thru load system into nozzle, out nozzle holes into accelerating well, to bowl fuel height

• Throttle opened rapidly, fuel flows out of nozzle tip, and out of well thru nozzle

• When empty, air flows thru vent and nozzle holes – leans mixture

Accelerating Well Vent

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TSX Idle System

• Slow idle– Manifold vacuum applied to

primary (top) idle hole• Large ∆P between fuel in bowl

and primary hole– Fuel forced from acceleration

well thru idle passage

– Fuel mixes with air at idle needle seat

• Additional air from secondary hole

– Proper air-fuel mixture flows from primary hole

• Fast idle – both primary and secondary holes flow

• NOTE: Idle Needle controls AIR, NOT fuel

Idle Air inlet

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TSX Economizer System

• Similar to DLT• Bowl vent air enters

around venturi• As throttle plate nears

economizer hole, manifold vacuum applied to redeconomizer passage– Economizer jet limits

air flow– Lowers pressure on

fuel – less fuel thru nozzle

• All carbs with load needle have econ jet– Some carbs without

load needle have jet

Economizer hole

Economizer jet

Bowl Vent air

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TSX Economizer System

• Similar to DLTX• Bowl vent air enters

around venturi• As throttle plate nears

economizer hole, manifold vacuum applied to redeconomizer passage– Economizer jet limits

air flow– lowers pressure on

fuel – less fuel thru nozzle

• All carbs with load needle have econ jet– Some carbs without

load needle have jet

Economizer hole

Economizer jet

Bowl Vent air

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TSX Service Information

• Separate top from bowl – 4 screws• Remove gasket, venturi• Word on jets

– Grind screwdriver to fit “perfectly”– Be gentle in attempts to remove

• If stuck and force, spread out edges which dig into casting –making it harder to remove

• Apply heat, let cool• Sometimes have to drill out

• For top– Remove float, check– Remove idle jet (at angle)– Check for economizer jet – deep in hole

• If present, remove

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• Top service, cont’d– Remove idle needle– Remove needle and seat– Remove throttle plate (note how located)– Check throttle shaft for looseness

• Wear on shaft – replace• Wear in shaft holes – usually no bushings

– Machine for bushings – can be tricky– Clean all passages (idle, economizer, vent)– Assemble with new gaskets, necessary parts– Set float ~level with top upside down

• Bowl service– Remove choke plate (note how located)

• Remove choke shaft, note how spring wound

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• Bowl service cont’d– Remove load needle if present– Remove bowl drain– Remove nozzle

• Some unscrew from venturi area• Some unscrew from bottom after remove needle• Again, use proper screwdriver and/or heat• Remove gasket on end of needle

– May be stuck in recess

– Clean all passages– Reassemble with new gaskets

• Assemble top to bowl• Check fuel level – 5/8” from top gasket

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Zenith TU Carburetors – Diesel Starting Engines

• Used first on 70D (Oct 1954)– R used Marvel Schebler SL-2 mixer

• Information available is inconsistent– Zenith catalogs and specification sheets

• O-11681 (AF2414R) used from 1954-57• O-12028 (AF2146R) was “service replacement”• O-12172 (AF3775R) used from 1957-1960

– Deere parts catalogs, MPI, …• AF2414R doesn’t exist• AF2146R used on 70D and 720D to 7214899

– Also on 80, 820 to 8203099• AF3775R used from 7214900 to end, and all 730

– Also on 820 8203100- end, and all 830

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Zenith TU Carburetors – Diesel Starting Engines

• AF3775R was replacement for others• 70D carburetor used “deflecting ring”

between throttle plate and manifold– Changed manifolds at 7034100

• Removed deflecting ring• Gone from then on

• All versions take K2067 kit– Gaskets, needle and seat– Anything more will be expensive

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Summary

• History of carburetor companies• Carburetor types• Carburetor systems and how function• Operation and servicing of popular units• Handout available

Handouts from the Gathering of the Green workshops are among the information included on the CD available through this web site.

gathering of the green 2008 winter conventionjd2cylservice.com/gog2008.pdf1 gathering of the green...

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