a history of the sportster

8/14/2019 A History of the Sportster

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A HISTORY OF THE SPORTSTERPart I

This article will be a chronological history of the overhead valve S ortsters that began in !"#$ andcontin%e to resent day& The history of this '%ch('aligned )half(brother) to the *ig Twin is intrig%ing&+aligned only recently by the %ninfor'ed& In yesteryear, this hot rod r%'bled with the best and %lti'atelywon the 'a-ority of street fights& The S ortster fo%ght the *ritish bi.es and the initial /a anese onsla%ghtfor s% re'acy on +ain Street in every A'erican town, in the ring at 0aytona Raceway or at the trac. forland s eed records at the *onneville Saltflats& It ran.s way ahead of the Evo, Twin 1a's and even theShovels in Harley fol.lore& The S ortster certainly rivals that of the legendary Panheads and 2n%c.s& Thero%gh and ready Hot Rod 34 fell into lace with the '%scle car era in the 5SA& It reverberatedirreverently, co%ghed, hac.ed and shoo. the gro%nd beside the big 6(78s o%t of 0etroit& This was'ainstrea' A'erica and its fascination for '%scle and do'ination at the sto light& So lets get a few'odern discri'inatory theories, racticed by so'e, o%t of the way&Real +en Ride S ortsersI say this in an historical conte9t since this co''ent wo%ld be inter reted today as se9ist in a variety ofways& :e all ride Harleys for s ecific sychological reasons b%t so'e legendary riders created the a%ra

that we all bas. %nder& 4et8s have a loo. at the eo le who defined and fra'ed the Harley traditions&:hen watching early bi.er 'ovies in the late si9ties and early seventies, yo% see the lReal 0eall ridingtheir beloved )1H8s) that today have beco'e living legends; It was a 'an8s world and these 'en didn8tsee a fe'inine side to anything they did& In the vernac%lar of the day )1H) is the acrony' for the br%tal,.nee(b%sting, .ic.(start 341H S ortster&The S orstser and the A'erican 0rea'These icons that for' this facet of the A'erican 0rea' e'body freedo' and a wild abandon that 'ostcan only fantasi


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high the rear fender was nearly scra ing the as halt& He deflated the re'aining wind o%t of 'y sails as heaccelerated ahead on one wheel&Entry 4evel +odelThis is -%st another Harley enig'a that feeds the fol.lore s%rro%nding the 6(Twin& Yo% need the legs of abas.etball layer to lant both feet flat on the gro%nd on one of these bi.es& They sit so tall& The .b%ddyl

seat %sed fro' !"#>8s well into the !"$>-s sits on to of the bi.e& In fact it sits off the bi.e& This thic.%nforgiving ad 'a.es one thin. that yo% are sitting in the stratos here&The S ortster was and is theentry(level bi.e designed to attract new Harley riders&The Factory Racing *i.eThe S ortster has been the Factory racer in differing events for over forty years now& This began in !"#?with the advent of the Flathead side valve 2 'odel that was the redecessor to the overhead valveS ortster in !"#$& These racers first .nown as the 2R and later as the 3R were the S ortsters that Harley0avidson sent o%t to defend the faith& These 'ean 'achines have do'inated Flat Trac. racing forever=yo% .now, where yo% go f%ll s eed aro%nd corners with no bra.es&Hillcli'bing is another ty e of racingthat S ortsters have do'inated&Then 1a'e *ronson)Then 1a'e *ronsonl was the first and only T6 Harley hero who traversed A'erica, 'eeting everychallenge society co%ld throw at hi' on his S ortster 341H&The *an. Robber8s 1hoiceIn the late seventies and early eighties, so'e ban. robber gangs even %sed the S ortster as a get awayvehicle=faster than the *ig Twin olice bi.es and 'ore ni'ble thro%gh traffic&Overhead Valves vs. Sidevalves

In !"#$, the 'odern overhead valve Ironhead S ortster was born fro' its redecessor the 2 seriesSidevalves also .nown as Flatheads& *%t first, what does all this Harley vernac%lar 'ean; Ironheadsdenote S ortsters 'ade fro' !"#$ to !"7#& The overhead valve Ironhead engine to (ends are'an%fact%red fro' cast iron as o osed to the 28s 'ade fro' !"#? to !"# that had al%'in%' finned)Flat) heads& The Evo 348s that were first 'an%fact%red in !"7 and contin%e to resent day haveal%'in%' )overhead valve) heads& +odern technology of the day dictated the %se of al%'in%' since itwas lighter for 'ore ower to weight ratio s eed& It also enabled 'ore efficient air(cooling with s% eriorheat dissi ation& Thirdly it is easier to wor. with and 'achine& *ig Twin Flatheads as well as thevenerable C# c%bic inch sidevalve 'odels nor'ally were o%tfitted with cast iron heads& The )s ort) orracing 'odels had al%'in%' heads that allowed these bi.es to o%tblast a t%rtle& *%t li.e the t%rtle, theFlatheads were d%rable and al'ost always got to the finish line& Harley went with cast iron to (ends onthe Ironheads -%st to lay safe& Alloy 'etall%rgy technology was available bac. then and was being %sedon the Panhead& However the Factory was having so'e roble's with the alloy Pan heads so it o ted forthe safer and 'ore co'fortable cast iron on the 8#$ S ortsters&Harley 6ernac%lar It is one of the D%ir.s of Harley 0avidson that each 'odel and es ecially each art see's to have at leastthree na'es& There is the official Factory na'e for a art that hardly any one ever %ses s%ch as )tri lecla' ) which denotes the brac.et that holds the for.s to the fra'e nec.& The 'ost co''on variation of

this Harleyese is the )crown) or )for. crown)& For. brace or brac.ets are other synony's& It gets 'oreco' licated as dialects of this lang%age e'erge when travelling fro' city to city& +ore na'es e'erge todescribe the sa'e bi.e or art& Pity the oor arts erson who has been ta%ght the correct na'es forthese ite's b%t now '%st learn all the slang in order to co''%nicate effectively with the Harley rider&The 2 Sidevalve FlatheadFlatheads were also called side(valves to differentiate the' fro' the overhead valve 'odels& The head isbasically a flat iece of cast iron with cooling fins rotr%ding at ">> % wards& There is a shallow indentationin the %nderside acting as a co'b%stion cha'ber& Fo%r se arate ca's act%ate the valves& The ca's arein the sa'e location as 'odern S ortsters located seD%entially side by side in the ti'ing cover near the


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botto' right side of the engine& In fact the first overhead valve S ortsters %sed the 2 botto' end as itslatfor' to 'o%nt the then 'odern to (end cylinders and heads& Incidentally, the Flathead *ig Twins also

had C ca's % %ntil the introd%ction of the overhead valve Panhead in !"C7& The Flathead )C#) whichstood for C# c%bic inches which is a ro9i'ately $#>cc8s is the longest lasting side(valve and was notdiscontin%ed %ntil !"$@& An overhead valve 'odel did not re lace the )fo%r(five)& The )2) Flatheadintrod%ced in !"#? was the s ort 'odel of the *ig Twin Flathead and the wor.horse C# ) fo%r(five& Thevalves are on the engine cylinder8s side& The valve ste' sitting on the rotating, ascending anddescending, ca'shaft egg(sha ed lobe act%ates the' via a solid ta et roller& Therefore %shrods arenot %sed or needed as inter'ediary transfer agents& The Flathead valves were located vertically ad-acentto the cylinder with the ste's down towards the ti'ing chest enclosed ca's& The t%li ed valve facesfaced % wards to a channel, which for'ed art of the co'b%stion cha'ber&Ergo the nickname Sidevalve.

This is '%ch the sa'e as overhead ca's fo%nd in the 6(Rod act%ating the valves directly& The differenceis that the side(valve is very inefficient ri'arily beca%se of co'b%stion cha'ber design& The otherdifference, of co%rse, is the ca' and valve locations being 'oved fro' the side of the engine to the to & Itis widely tho%ght that the 2 series Flatheads were discontin%ed after !"# with the introd%ction of the 34in !"#$& However the Flathead 2 racing 'odels contin%ed on for another !> years& These 'odels werecalled the 2R C# c&i& Trac. Racer, flat trac.er , the 2R TT C# c&i& and the 2HR TT ## c&i&, To%rist Tro hRacers& 1al Rayborn the fa'o%s Factory racer won the 0aytona ?>> 'ile on a 2R TT in !" 7 with as eed of !>! 'iles er ho%r& He tri%' hed the English and /a anese while s%rro%nded by 'oderntechnology&The first 34R TT overhead valve racer first a eared in !"#7&Engine Si> 34H re laced the !!>>, again %tili)& This a bigincrease in stro.e and red%ces engine longevity& The e9tra 2 stood for a Factory o tion of a )s eed)

ac.age& Horse ower increased to @7 HP and a to s eed of "#' h& The trans'ission gears had to be


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strengthened as this owerho%se ro%tinely .noc.ed teeth off the gears&The addition of the letter Hrobably referred to High 1o' ression or High Perfor'ance b%t here are those that feel it 'eant Hot,

Heavy 0%ty or 'y favorite Hell on :heels& These ri'itive Flatheads staved off the *ritish invasion ofTri%' hs, *SA8s and Bortons for 'any years on the race circ%it& The first !"#$ 34 77@cc 'edi%'co' ression 'odel rod%ced C> HP at ##>>r ' with a co' ression ratio of $J!& In !"#7, two new'odels were introd%ced with an increased co' ression ratio of "J! and bigger head orts and valves&The 34H andthe off(road scra'bler, the 341H rod%ced C# HP& The 34R racing 'odel really % ed theante in the race circ%it a it shed !C> lbs& and increased the HP to 7>& For the day, this e9tre'e ower toweight ratio was heno'enal& In fact an 34R engine set a world s eed record of ? # ' h at the*onneville Salt Flats in !"$>& In !"$? with a dis lace'ent increase to ! c&i& or !>>>cc the officialhorse ower was rated at ! with a co' ression of "J!& It is interesting that this 'odel rod%ced ! HP erc%bic inch, which 'any Harley engine b%ilders today fail to achieve& The Edsel of the Harley world, the!"$$ 341R 1afK Racer did even better rod%cing 7 re %ted horse ower fro' its "J!, ! c%bic inches&There was nothing wrong and a lot right with this 'odel b%t its styling was too far o%t for traditionalthin.ing Harley riders& The following fig%res for the vario%s Evo S ortsters vary by a few horse ower fro'year to year beca%se of incre'ental changes in design& The Evol%tion 77@ S ortster rod%ced only ##horse ower& The !!>>cc 6? 34H 'ade @ horse ower with an increased bore and 7J! co' ression&The !?>>cc Evo increased horse ower to the # to range& It did this by increasing the bore a

heno'enal !G?)over the 77@cc 'odel by boring o%t the sa'e cylinders +odified heads also contrib%tedto this increase& The hot rod !?>>S only % ed it a few 'ore to the " HP range& Re'ove the oll%tioncontrols fro' this baby and it flies relative to other 34 'odels&:hat They 1ostThe !"#? 2 cost L7 #&>> a 'ere L!!#&>> less than the *ig Twin F4& !"$> 28s were rod%ced while only!$ 2R8s, the racing version, were 'ade in !"#?& The 8#$ 34 cost L!!>@&>> while the F4 was only L C&>>'ore at L!! $&>>& This very low rice differential, es ecially when co' ared to today where a *ig Twincan cost @ ti'es that of a S ortster, attests to the o %larity and res ect co''anded by this early legend&Be9t +onthIn this '%lti( art historical series, we will be e9a'ining the S ortster8s develo 'ent both 'echanicallyand erce t%ally to the resent day& Be9t 'onth we will begin with the 'echanic8s drea', the Tra 0oor&This innovation 'ade reb%ilds e'inently easier& It ta.es a very s.illed 'echanical artist with the )feel) toreb%ild the re tra (door 'odels&The articles e9 ress the o inions and views solely of 0onny Petersen& They are not intended in lace ofor to diagnose or resolve any iss%e not assessed by a D%alified technician& 0onny Petersen and Heavy0%ty 1ycles 4i'ited does not ass%'e and e9 ressly disclai's any liability with res ect to the %se of, orfor da'ages res%lting fro' the %se of any infor'ation, advice or reco''endations within& Reference toany rod%ct, rocess, %blication, service, or offering of any third arty by trade na'e, 'an%fact%rer orotherwise does not constit%te or i' ly the endorse'ent or reco''endation of s%ch by 0onny Petersen,Harley(0avidson or Heavy 0%ty 1ycles 4i'ited& E& M O& E&

The Overhead Valve Ironhead

The S ortster and it8s redecessor the )2) fro' !"#? to the resent day has fo%r se arate ca's, each ofwhich has one lobe for each se arate valve& The ca' for a !""" and earlier *ig Twin has fo%r lobes on it,

one for each of the fo%r valves, two of which are located in each head, one inta.e and one e9ha%st& The34 syste' is s% erior to the *ig Twin in that the angles of each lobe are 'ore directly %nder the valvetrain& The *ig Twin lobes are located centrally in the ti'ing cover 'eaning that the e9ha%st valves locatedat the front of the front head and at the rear of the rear head necessitate a severe angle change in thevalve train& This can ca%se so'e annoying roble's s%ch as a ersistent tic. ca%sed by hydra%lic lifter)bleed down)& The T1778s d%al ca's corrected this roble' in !""" b%t the S ortster and 2 had it beatsince its ince tion over #> years earlier& The 6(Rod has overhead ca's directly act%ating the overheadvalves eli'inating the need for a valve train& The only reason for a valve train is that the ca's are locatedaway fro' the valves and lin.age is needed to -oin the two& On all 28s and S ortsters the ca's arelocated inside the ti'ing cover -%st below the carb%retor&


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The Overhead 6alve TrainThe valve train is owered by a gear on the inion shaft which is an e9tension of the rotating flywheels,

cran. & This inion gear is connected directly to a gear on the end of the rear head8s inta.e ca'& Therear inta.e ca' has another gear on it that 'eshes with thereby rotating both the rear e9ha%st and thefront inta.e ca's& The front inta.e ca' also has an additional gear that connects with and rotates thefront e9ha%st ca'& The circ%it brea.er ignition or 'agneto ignition drive gear, as the case 'ay be, alongwith the idler gear that drives, rotates , the generator are also driven by a ca' gear& As the rear inta.eca' gear rotates in tande' with the t%rning cran., the egg sha ed ca' lobes rotate& The ta et, lifter ,has a roller on one end which follows the ascending or descending ca' lobe& This forces the lifter % anddown %lti'ately o ening and closing the valves, which lets the airGgasGe9ha%st in and o%t& This, in t%rn,creates the ower that ca%ses the cran. rotation& As the lifter is forced % , it %shes % the %shrod,which fits into one end of the roc.er ar' inside the roc.er covers or wafers& The roc.er ar' oscillatesbac. and forth on a shaft so that the other end %shes down on the valve ste' to & This actionco' resses the valve s rings by %shing the valve ste' down and thereby o ening the valve& The nowdescending ca' lobe rela9es its % ward ress%re& The co' ressed valve s rings are allowed todeco' ress and force the valve to close& The valve train 'erely follows the directions of the rotating ca'lobe as it8s grad%ated high s ot forces the train to ascend o ening the valve& The low s otcorres ondingly allows the train to descend thereby closing the valve& The ter' valve train is really a'isno'er& There are act%ally C se arate valve trains& Each of the fo%r ca' lobes has a se arate valve

train or lin.age connecting it with the valve it o erates&The Engine 1ase S% ort Syste'The ca's rest side(by(side in the right side ti'ing case located below the carb%retor& The C ca'shaftsrest in b%shings located in the ti'ing cover on one side& The other ends of the ca'shafts are s% ortedby caged Torrington bearings on the o%tside of the right hand engine casing& The two longit%dinally s litcase halves enclose the engine cran. or flywheels& The o%tside of the left casing with its 'ating ri'arycover ho%se the ri'ary drive syste' co' osed of front engine s roc.et, a cl%tch shell s roc.et and theconnecting ri'ary chain& The f%nction of the ri'ary is to transfer ower fro' the engine thro%gh thecl%tch to the trans'ission& The trans'ission has C s eeds fro' !"#? to !""> and # s eeds fro' !""! tothe resent& Each s eed has a different gear ratio that allows the bi.e to accelerate to higher s eedswhile controlling the cran.shaft revol%tions, r '8s & Inside the cl%tch shell we 'entioned earlier rests thecl%tch whose f%nction is to transfer or engage the engine ower thro%gh the trans'ission to a chain orbelt connecting the rear wheel& The second f%nction is for the cl%tch to disengage the engine ower fro'the trans'ission and therefore the rear wheel by releasing ress%re on the cl%tch lates&5nit 1onstr%ctionThe 2 and 34 casings li.e the antiD%ated *ig Twin design ho%se the engine cran. and ca' s & Howeverthe S ortster syste' also encases the ri'ary drive syste', cl%tch and trans'ission& *ig Twins have ase arated engine, ri'ary driveGcl%tch and trans'ission& The 6(Rod %ses )%nit constr%ction) si'ilar to the2 and 34& I-ll digress f%rther& The 2n%c., Pan, Shovel and Evo *ig Twin engineGtrans'ission co' onentsfle9 and lac. rigidity& The torD%e fro' the 'otor botto' end wants to fle9 one way, as does thetrans'ission drive, which wants to go the other way& The ri'ary casings have to connect the two and'a.e a feeble atte' t at controlling all these o osing forces going on& After all, the only f%nction the

ri'aries sho%ld have is to ho%se the internal co' onents washing the' in an oil bath and .ee ingo%tside dirt fro' abrasively da'aging the wor.ing arts& This roble' was fi9ed with the Twin 1a' 778s&The T177 beca'e the first *ig Twin to a roach %nit constr%ction by directly bolting the engine casing tothe trans'ission casing effectively 'a.ing the' a single b%t se arate %nit& Rigidity is a the'e that

ervades the T177& This translates into better handling, reliability, d%rability and one to%gh 'achine&*ac. to the '%ch 'aligned S ortster& 5nit constr%ction has been a the'e since day one in !"#? with the.2l 'odel&Rigidity has always been the way for the 34& It is one reason that this 'odel is the traditionalhotrod of the Harley world& The 6(Rod while not correctly called a *ig Twin %ses %nit constr%ction for allthe reasons listed above&The *ig Twin has always allowed easy access to the trans'ission& This was notalways so for the early 28s& *efore the 34 evolved o%t of the 2, the engineers blessed %s 'echanics byallowing the sa'e easy access for re airs and gearing changes thro%gh redesign of the %nit constr%ctioncases&


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The Trap Door

+y research indicates discre ancies when the tra door trans'issions were instit%ted& So'e say in !"# &Other research indicates that it ha ened in !"#C& :ell I owned a !"#@ 2 which didn8t have one and norwas it s% osed to& I also owned a !"## 2H or 2H2, I can8t re'e'ber which, and it didn8t have a tradoor either& It8s entirely ossible that so'e or all !"#C and l"## 28s didn8t have tra doors while others did&Harley 'ay have been %sing % a s%r l%s of the older non(tra door casings while instit%ting the designchange&This ty e of arts overla was very co''on bac. then when asse'bly line wor.ers had '%ch'ore 'echanical re air and )what will fit what) seat of the ants .nowledge& It wo%ldn8t be tolerated on a'odern 'an%fact%ring line& The Tra door is located in the left trans'issionGengine casing behind thecl%tch shell in the ri'ary& The addition of a tra door si' lified reb%ilds considerably allowing easieraccess to the trans'ission after re'oving the cl%tch asse'bly and .ic. start gears fo%nd inside the

ri'ary casing on the left side of the bi.e& After re'oving the s roc.et cover behind and ad-acent to theti'ing cover on the lower right side of the engine, the wrench is able to re'ove the trans'ission rearchain s roc.et& This allows the co' lete trans'ission and tra door to be re'oved fro' the left side ofthe bi.e& :hy was this s%ch an a reciated advance'ent in engine design; Prior to the tra door, theengine casings had to be )s lit) to allow trans'ission re'oval& This, of co%rse, 'eant the whole enginehad to be disasse'bled& F%rther'ore, gear s acing, case to gear end s acing and shifter for. align'enthad to be done and tested for correct fit'ent by re eatedly asse'bling and disasse'bling engine casingsand trans'ission co' onents& This was e9tre'ely s.illed wor. that few 'odern technicians are ca able

of since it is a long way fro' si' le arts re lace'ent& Of co%rse the old Harley dawgs are bef%ddledwith 'odern engine 'anage'ent syste's so it wor.s both ways& There is art and science involved inreb%ilding so'e of these older Harleys& *efore we e9 lore the S ortster trans'ission which didn8t changethat '%ch fro' !"#? to !""> with the advent of the #(s eed in !""! lets loo. at an early roble'enco%ntered for the first twenty years&The Speedo Drive

5nit constr%ction has a 'a-or drawbac. in that if the casings need to be re laced it beco'es costrohibitive& Of co%rse, if they are ro erly loo.ed after, they won8t ever need re lacing for the life of the

'otorcycle& On S ortsters % %ntil and incl%ding !"$?, the s eedo'eter drive r%ns off the co%ntershaftlow gear in the trans'ission& The drive is inserted thro%gh the trans'ission casing with a beveled rotatinggear on the end that 'eshes with the low gear& A cable is attached which of co%rse goes to thes eedo'eter& The s eedo drive gear rotates the inner art of the cable, which rotates the 'echanis' inthe s eedo head to o erate the odo'eter and s eedo'eter& The *ig Twin had a si'ilar set% %ntil !"$?that was and is very reliable& In !"$@ the Factory went to a front wheel s eedo drive on all 'odels, whichit %sed to the advent of the electronic %nit circa !""# de ending on the 'odel& Harley has had a lot oftro%ble with s eedo'eters over the years& The front wheel 'echanical drive %nit was and is fli'sy& It isalways screwing % beca%se of sei


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A a!or Vi"ration Improvement

+odern S ortsters vibrate a lot b%t very little in co' arison to the early vintages& This i' rove'ent invibration red%ction is ri'arily d%e to better and 'ore recise 'an%fact%ring 'ethods, i' roved enginebalancing and taller gearing& The latter ins%res that the engine is not revving as high es ecially on thehighway& Early S ortsters %sed low s roc.et gearing designed for fast city riding b%t were br%tal on thehighway& The first thing we do with older S ortys in o%r sho is to e9a'ine if the stoc. gearing is stillbeing %tili


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Ignition S#stems &+&

:hat goes aro%nd co'es aro%nd& In the early nineteen h%ndreds, one of the biggest h%rdles the internalco'b%stion engine had to overco'e was to fig%re o%t how to control co'b%stion& This is also one of the'ain S ortster iss%es in ?>>@=&how to control inging an %ncontrolled for' of co'b%stion& A constantrate )ti'e(release) b%rn was reD%ired instead of ha ha,>>> and C>,>>> volts fro' the battery8s ca acity of either or !?

volts& The transfor'er )ste ing % ) the voltage is, of co%rse, called the coil or 'ore ro erly the ignitioncoil& The high voltages are reD%ired to fire the s ar. l%g& The firing occ%rs when the voltage -%' s orarcs across the air(ga between s ar. l%g electrodes& It is easy to fig%re o%t the s ar. l%g air(gaad-%st'ent& The lower the ste ed % voltage the narrower the ga '%st be& The Points Ignition electricalstorage facility .nown as a condenser cannot store 'ore than ?>,>>> volts witho%t lea.ing -%ice&Therefore its res ective s ar. l%g air(ga is set at &>?#(&>@>), ?# to @> tho%sandths of an inch & Theelectronic ignition '%st b%rn a leaner 'i9t%re of f%el to 'eet e'issions controls& There is '%ch 'ore airthan gas relative to the days where oints and 'agneto ignitions reigned& This lean 'i9t%re easilycontrib%tes to the 'odern inging roble'& :e need a hotter s ar. to ignite this lean f%el 'i9t%re&Storage of electricity is not a concern with solid state co' onents and a transfor'er with increasedinternal coil windings rod%ces aro%nd C>,>>> volts of electricity& S ar. ga can be increased to &>@7) to &>C@) Ignition triggering is ca%sed by either a 'oving 'echanical switching device s%ch as oints or by asolid state(switching %nit s%ch as the electronic %nit&

Sportster Ignitions

In general the distrib%tor ignition was %sed fro' !"#? to !"## on the street rod%ction 2 Flathead 'odels& After !"#7, 'agnetos beca'e standard on 'ost 341H8s %ntil their de'ise in !" "& I %se general ter'ss%ch as )in general, 'ost and so'e) beca%se nothing was written in stone in the early years& +odern'an%fact%ring 'ethodology does not tolerate this where every 'odel Harley is identical to the ne9t& *oththese syste's were e9ternal and were located -%st above the ti'ing cover, beside the front cylinder on


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the right side of the engine The year !"$> bro%ght the advent of ti'ing cover redesign to incor orate theoint8s ignition internally inside the cover& This lasted another eight years %ntil electronic ignitions 'ade

their deb%t in the sa'e covers in !"$7& The S ortster switching device, oints or electronic , is driven offthe end of one of the C ca'shafts fro' !"$> to ?>>@& !"#? to !" " 28s and S ortsters were driven via ashaft, internally, off the s%bsidiary circ%it brea.er drive gear owered by a ca' gear& The sa'e basicti'ing cover design is %sed to ?>>@ %tili


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Changing Timing e/$irements

0ifferent 'odels and years have different settings de ending on oll%tion control reD%ire'ents if any ,variables s%ch as iston s eed, ignition syste's, cylinder bore si>@!?>>S have d%al l%gged heads& Ignition ti'ing reD%ires less advance ti'ing as the res ective fla'efronts have less distance to travel&Other things being eD%al an 77@ 34 needs less advance ti'ing than an!!>> S orstser, which needs less than a !?>>cc 'odel& The !!>> and !?>> achieve their greater si


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co%ld be fo%nd in a 8#$ 1hevy& Re'e'ber I a' tal.ing abo%t ?# to C# years ago where tractors and 8#$1hevies were very co''on&

The Points Ignition

Electrical arcing destroys oints or least reD%ires a re air& Arcing occ%rs when a bi.e is 'isti'ed and thecondenser releases -%ice at an ino ort%ne ti'e& Fa%lty condensers also )lea.) -%ice& After the bi.e is

ro erly ti'ed andGor the bad condenser is re laced the arc da'age re air is si' le& A oints file %sed tobe a sta le of any tool ac.& In those days, he who had no tool ac. didn8t get to where he was going&This is the fli side of 'odern irre arable arts& Yo% have to re lace the' b%t very infreD%ently&*rea.downs on a new S ortster are al'ost non(e9istent today& Bo oints file; Bo roble'&

r. Fi1it

:e all s'o.ed cigarettes in those days and we all carried 'atches& Bo 'atches; That8s cool too& Therewere always discarded e' ty 'atchboo. covers lying on the gro%nd everywhere& :e didn8t need the'atches& :e needed the cover and the abrasive stri that the 'atches were str%c. against& :e toreaway the stri and voila8 we had a oints file to clean % any itting on the oints s%rfaces& Oily oints;0i the 'atch cover inside the gas tan. and then r%n the gas soa.ed stri between the oint faces toclean the offending oil& :hen filing, 'aterial is re'oved which increases the oints ga =&&not that theywere ever recisely ga ed for '%ch of the ti'e anyway& +ost 'atch boo.s a er thic.nessa ro9i'ated the thic.ness of the reD%ired oint8s ga & It then beca'e a tool called a feeler ga%ge thatsho%ld have been religio%sly .e t in the bi.e8s tool ac.& 0%ring a it sto the ti'e(honored gag was to

%t a 'atchboo. cover between the oints on yo%r b%ddies bi.e when he wasn8t loo.ing& Then everyoneelse sat down, lit a cigarette and watched with sadistic a'%se'ent as yo%r b%ddy .ic.ed his bi.e overand over and over to total e9ha%stion& Of co%rse, yo%r t%rn ca'e soon eno%gh to be the b%tt of the ne9t

-o.e& E9 erienced 'echanics of the day had 'icro'eter eyes that co%ld set vario%s oints ga s of &>??)and &>!7) by eye& If yo% were o%t a co% le of tho%8, no biggie&Correct Points Ad!$stment

Points are ad-%sted when the oint8s ignition distrib%tor ca' rotated to a high oint thereby holding theoints in the o en osition& The narrow lobe on the oint8s ca' is for the front cylinder while the fatter

lobe is for the rear& A 'eas%re'ent that 'any wrenches didn8t do was to co' are the oints ga for bothnarrow, front cylinder , and fat, rear cylinder oints ca' lobes& It was 'ore i' ortant that they didn8tvary by 'ore than C tho%8, &>>C) fro' each other& If a !"$>($7 front cylinder oints ga was set reciselyat the reD%ired &>!7) , !7 tho%8 then the rear lobe setting sho%ld be in a erfect world also at &>!7)& Thisnever ha ened so the goal beca'e between &>!C) and &>??)& +ore than this indicated arts were wornand needed re lace'ent es ecially on the e9ternal !"#?(!" " shaft drives& :hen tolerances were o%t onthe internal !"$>($7 ca' drive oints syste's, the roble' is %s%ally a 'isalign'ent of arts, which caneasily be corrected& On !"#? to !"$7 'agneto and oints ignitions, one ar' of the oints is fi9ed to the'agnetoGdistrib%tor base by a hold(down screw& The other ar' is s ring loaded so its oint8s face wo%ldrest against the fi9ed oint8s face& The 'oveable ar' has a fiber attached to it that rides on the distrib%tor

oints ca'& On !"#? to !" " 'agnetoG oints ignitions, the oints ca' is the to art of the distrib%torshaft that e9tends thro%gh the front area of the right hand engine casing connecting the oints late to therotating circ%it brea.er drive gear& This is owered by a ca' gear, which is %lti'ately owered and t%rned

by the rotating flywheels via the inion shaft& If the oints faces are set too closely, the bi.e will r%n oorlywith lots of bac.firing thro%gh the carb%retor& If so close they are to%ching, it revents the bi.e fro'r%nning at all& If ad-%sted too wide the bi.e r%ns ro%gh %ntil not at all& The !"$>(!"$7 S ortster ointsignition is a '%ch 'ore co' act syste' that o erates on the sa'e rinci les as the earlier versions& It isalso owered by a rotating oint8s ca' b%t it is attached directly to the end of one of the C engineca'shafts by a long thin bolt&


12/30

The %roken %olt

It is a oor hold(down design in that the bolt head is a half(inch while the ste' has a tiny dia'eter& Thehold down bolt will often brea. off leaving a iece st%c. inside the end of the ca'shaft and conseD%entlya 'otorcycle that won8t r%n& Even rofessional 'echanics brea. this bolt& So'eti'es the bolt threadsadhere too well to the 'ating ca' threads via loctite or o9idation, r%st & The t%rning torD%e reD%ired tofree and t%rn o%t the bolt e9ceeds the torD%e that will brea. the bolt& So'eti'es if tightened -%st shy ofbrea.ing, the bolt will sna on the road after the 'ating arts have heated % and e9 anded therebysna ing the bolt shaft& Nive an a'ate%r a half(inch wrench and a brea. ha ens every ti'e& 0rilling o%tthe bro.en bolt is tric.y, recise and annoying& Screw % , which is easy to do, and the ca' threads arer%ined necessitating the ca'8s re lace'ent&

an$al and A$to Advance Timing

Fro' !"#? to !" # the distrib%tor has to be 'an%ally retarded by cable thro%gh twisting the left(hand grifor easier starting& 0itto with 'agnetos& As the bi.e gained s eed the o erator wo%ld twist the 'an%aladvance gri the o osite way in order to advance the ignition ti'ing& In ractice, this a%to(retard ti'ing'echanis' wo%ld brea. over ti'e& A lot of riders wo%ld 'an%ally ad-%st the distrib%tor or 'agneto byleaning over and hysically 'oving the %nit bac. for starting& After the bi.e was war'ed % , the riderwo%ld 'an%ally advance it by hand before ta.ing off& +any ti'es a s ring wo%ld be -%ry(rigged to hold thedistrib%tor or 'agneto in osition& In !" #( % %ntil !" " de ending on the S orty this all changed& The

distrib%tor ignition ti'ing roced%re beca'e a%to'ated& :hile different arts were %sed the !"$>(!"$$oints syste' %sed the sa'e a%to'ated syste', as did the earliest electronic ignitions in !"$7 and !"$"&This a%to'ated syste' %tili


13/30

D$al 3 Single Fire

All S ortster ignitions with the e9ce tion of one fro' !"#? to resent are d%al fire, which has a wastede9tra s ar. & The s ar. l%g goes off as it is s% osed to so'ewhere towards the end of the co' ressionstro.e& It also goes off on the e9ha%st stro.e as s ent gases are leaving the engine via the o en e9ha%stvalve& Single(fire is what it says& The s ar. l%g only goes off when it is s% osed to& The rest of theworld reali>S hot(rod S ortsters first and then to EFI 'odels and Twin 1a's&Concl$sion

Be9t 'onth in The History of S ortster Part I6 we are going to loo. at the Factory8s atte' ts at bridgingthe traditional Harley 'ar.et into 'ainstrea' 'ass 'ar.ets thro%gh a variety of S ortster 'odels& Thenwe8ll loo. at so'e 'ore 'echanical st%ff& The editor is robably going to c%t 'e off after C seg'ents onthe S ortster b%t I co%ld go on for , $ or eight&

Ignition Timing

I don4t $nderstand 0hat advance or retard means or 0h# ignition m$st "e timed. 5o pro"lem. First

6et7s $nderstand t0o principles o2 setting the gas on 2ire inside #o$r engine8 0hich are9com"$stion lag9 and 9controlled "$rn.9

Com"$stion 6ag

Once #o$7re hip to this. :o$7ll "e hip to advance and retarded ignition timing 0hich is "asicall#0hen the spark pl$g ignites the air;gas mi1t$re.

It takes time 2or the gas to "$rn 0hich o"vio$sl# creates heat and the e1pansion o2 this heatcreates press$re to 2orce the piston do0n to t$rn the 2l#0heels 0hich ca$ses the po0er train tot$rn the rear 0heel. TDC?8 as 2ar $p as it can go compressing the air;gas mi1t$re on the compressionc#cle or stroke 0hen the spark pl$g goes o22. This means that ignition timing is at +@ 0ith noadvance or retard.


14/30

In act$alit#8 ignition occ$rs "e2ore the piston reaches top dead center8 >%TDC?. on thecompression stroke.

ATDC A2ter Top Dead Center

a1im$m com"$stion occ$rs a2ter top dead center8 >ATDC?. This means that the spark pl$g goeso22 "e2ore the piston has 2$ll# compressed the air;gas mi1t$re and "e2ore the piston has reached

top dead center. This is 0a#8 0a# "e2ore the piston is on it7s 0a# do0n in the po0er stroke.Fo$r Stroke

:o$r


15/30

top dead center. This is calc$lated "# s$"tracting the (@ to @ retard allo0ance 2rom the stockB+@ advance setting.

Stroking and Timing

Stroking means the piston m$st move 2$rther $p the c#linder and do0n the c#linder in the sameamo$nt o2 time. There2ore8 depending on ho0 radicall# the stroke is increased8 the ignition timing

m$st "e advanced accordingl#. emem"er that the gas "$rns at a controlled rate. There2ore itm$st "e ignited sooner in order to "e completel# "$rned as the piston is "eing p$shed do0n thec#linder "# e1panding heat and press$re on the po0er stroke.

%ig %ore and Timing


16/30

"e le2t $p to technical e1perts especiall# i2 #o$r engine has "een modi2ied. Once e1plained this isa prett# eas# s$"!ect that can get real complicated real 2ast

Donn# Petersen


17/30

:hen all the co' le9 -argon is stri ed away, an ignition syste' rod%ces a s ar. at the s ar. l%g torod%ce a controlled b%rn of the airGgas 'i9t%re at the right ti'e to %sh the iston down with o ti'alower to t%rn the flywheels which %lti'ately t%rns the rear wheel&

+ost eo le thin. that the airGgas e9 lodes as o osed to b%rning in a controlled 'anner& This wo%ld

destroy the engine in short order& :hen internal co'b%stion engines were first invented the gas dide9 lode and this was a big roble' to overco'e since it red%ced engine life to virt%ally


18/30

0igressing for a 'o'ent, these rev li'its are one of 'any reasons that Evos last longer since the revscanQt esca e safe bo%nds artic%larly while the engine is brea.ing in&

+any hi( erfor'ance ignition control 'od%les or )brains) have 7>>> r ' rev li'its incor orated in the'li.e the Screa'ing Eagle ones& If yo% thin. abo%t it& This is st% id since no Harley I ever rode was

ca able of going 7>>> r 's& These arts are eli'inating a safety feat%re&

0iagra' !J Stoc. Harley d%al fire ignition syste' in which one brea.er oint and single ignition coil firel%gs in both cylinders at the sa'e ti'e, ca%sing a )wasted) or ) hanto') s ar. on the e9ha%st stro.e,

res%lting in vibration beca%se the 'otor wor.s against itself&

+ore so histicated 'od%les have ad-%stable rev li'its which can be set -%st above the %seable ower

band of the bi.e to revent in-%ry fro' a screa'ing engine ca%sed by a blown shift&5ninitiated Harley street racers wind o%t their scooters ast the increasing %seable horse ower rangebefore shifting into the ne9t gear for 'ore go forward ower&

Yo% hear these warriors all the ti'e winding o%t their oor iron horses, drag i es -%st )a bla,>>>volts&

:HY IS THIS;


19/30

:ell, oints and the storage %nit for b%ilt % electricity .nown as a condenser can only handle abo%t?>,>>> volts of -%ice before the condenser starts lea.ing electrons which will b%rn o%t the oints conf%singthe s ar. l%g all to hell abo%t when itQs s% osed to fire& To %t it 'ildly this decreases s ar. intensity awhole lot&

The s ar. l%g ga , which is the distance between the two electrodes on the end, is set narrower, atabo%t &>?7 tho%sandths of an inch , than the electronic ignition ga and a higher gas to air ratio, richer ,is %sed so the controlled b%rn can occ%r with less s ar. intensity&

This is the way it is beca%se this is all the oints syste' can handle&

This high 'aintenance set% was o.ay in the old days before oll%tion controls b%t as we all .now,environ'ental concerns dictated that less e'issions be rod%ced by gasoline engines&

SO, HO: 0I0 THEY 0O THIS;

The engineers designed ignition syste's to ignite a leaner gas ratio i&e& a higher air to gas ratio& To dothis, s ar. l%g ga s were increased fro' abo%t &>@7) to &>C@) tho%Q and a higher voltage of abo%t C>,>>volts was generated to -%' this greater ga &

Bow yo% .now the ri'ary reason Harley went to an electronic ignition& To b%rn 'ore of the gas torod%ce less har'f%l e'issions& This is also why gasoline 'an%fact%rers sto ed %sing lead as an

octane booster since lead ca%ses 'ental retardation in .ids& They switched to safer octaneQs li.e'anganese which only ca%ses cancer in .ids when they grow % &

The advantages in the newer Harley technology which is old technology to everyone else is that the bi.ebeco'es 'ore reliable, faster and is chea er to r%n in ter's of gas&

Yo% can fig%re o%t so'ething else now&

The reasons not to 'i9 a oints coil, ?>,>>> volts , and an electronic coil, C>,>>> volts , are beca%se anelectronic one will b%rn o%t oints re'at%rely and a oints coil cannot generate the voltage reD%ired to

-%' the increased s ar. l%g ga on an electronic syste'&

+any do it yo%rselfers neglect to change the coil when retrograding or % grading their scoots& And thenwhat do they do; :ell, bla'e the' cra y after'ar.et arts, of co%rse&

1o'e to thin. of it& IQve watched 'any a trained 'echanic do the sa'e thing where the oor artsbeco'e the whi ing boy for their own inadeD%acies&

The second art of s ar. intensity is called d%ration, or how long the s ar. is 'aintained for& This isi' ortant beca%se the airGgas '%st be ro erly ignited to allow the fla'e to travel to the far reaches of


20/30

the co'b%stion cha'ber and to rod%ce the highest ercentage of b%rn ossible& +ore on this in afollowing article when we will de'ystify ignition ti'ing((when the s ar. occ%r((as it relates to this s%b-ect&

*%t as a ri'er, advanced ignition ti'ing si' ly 'eans that the s ar. l%g ignites the gas earlier on andretarding 'eans the o osite, igniting it later& And again, this is done to 'a9i'i


21/30

:ell, a Harley is a fo%r stro.e engine which 'eans that the iston in each cylinder 'oves % and downfo%r ti'es to co' lete one f%ll cycle whereas a two stro.e 'otor only reD%ires the iston to 'ove % onceand down once to co' lete a f%ll cycle&

The fo%r stro.es areJ

inta.e stro.e where the iston 'oves down with the inta.e valve o en and the e9ha%st valve closed& Thiscreates a vac%%' thereby s%c.ing in the air and gas 'i9t%re&

co' ression stro.e where the iston 'oves % the cylinder with both inta.e and e9ha%st valves closed&This co' resses the air and gas 'i9t%re to better b%rn as the s ar. l%g ignites the 'i9t%re as the istonnears the to of the stro.e&

ower stro.e where the iston is now forced down by the e9 anding controlled b%rn with both inta.e ande9ha%st valves closed& The octane in the gas controls the rate of the b%rn in order to ro erly ti'e thevario%s seD%ences&

e9ha%st stro.e where the iston 'oves % the cylinder with the inta.e valve closed and the e9ha%st valveo en to e9 el the b%rned gases o%t the e9ha%st ort into the e9ha%st i es&

The ower stro.e .ee s the heavy flywheels, *ig Twin flywheels weigh @# lbs& , s inning to co' lete theother three stro.es to get to the all i' ortant ower stro.e again&

Bow yo% .now why the flywheels are heavy so that ower ind%ced 'o'ent%' and inertia gets the engineto the ne9t ower stro.e&

ItQs obvio%s that the s ar. l%g sho%ld go off -%st as the co' ression stro.e ends and the ower stro.esbegins and that there is no need for any fire in the hole d%ring any other art of the fo%r stro.es=right;Right

Yeah, b%t on yo%r 'odern Harley, this ainQt so e9ce t for EFI 'odels&

Yo% see, the s ar. l%g goes off twice on yo%r Shovel, Ironhead or Evo(((once when itQs s% osed tonear the end of the co' ression stro.e and once when there is no need for it on the e9ha%st stro.e&Hence the ter' d%al fire&

Bow, isnQt this strange& :hy wo%ld ignition syste' engineers try to b%rn s ent e9ha%st gasses;

In the old days when these ignitions were designed, Poll%tion controls werenQt the b%rning iss%e they aretoday&


22/30

Initially, the 'an%fact%rers were only trying to econo'i


23/30

A res ected Borth A'erican 'anager of Honda e9 lained to 'e that his biggest roble' in designingand 'ar.eting the Honda Ace was trying to e9 lain and rationali


24/30

They areJ

4ess vibration& The engine is wor.ing har'onio%sly with all the arts wor.ing in tande' instead ofwor.ing against each other& It '%st be noted, however, that the vibration will not be eli'inated=-%stred%ced since the %neven firing of the cylinder contrib%tes the 'ost to vibration&

*etter gas 'ileage& +ore forward ower is rod%ced beca%se the hanto' or wasted s ar. is eli'inated&The increase is 'ini'al b%t noticeable&

4onger engine life& The 'otor is not wor.ing against itself& Again the increase is not dra'atic b%t isnoticeable&

Horse ower increase& The increase is s'all b%t 'eas%rable&

Easier starting& The s ar. l%g goes off only when it is ti'e to create ower&

Precise /etting& 1arb%retor -etting can be dialed in 'ore recisely since engine t%ning is not bastardi


25/30

HarleyQs habit of following way behind which is good in traditional as ects b%t not so hot for bettererfor'ing and f%nctioning rod%cts&

Therefore, an ab%ndance of to flight single fire syste's are now available that blow away the stoc. b%tres ectable Harley d%al fire syste's&

The ne9t iss%e of Heavy 0%ty Bews will delve into the advance(retard ti'ing 'echanis's for 'orebac.gro%nd infor'ation to allow ro er choice of arts for yo%r reD%ire'ents&

And weQll loo. at so'e of the s% er d% er single fire ignitions& See yo% ne9t 'onth&

0onny

Postscri tJ IQve -%st had a chance to loo. at the Factory !""7 line% and in artic%lar the 34 !?>>SS ortster& This hi( erfor'ance 'odel feat%res d%al l%gging, higher co' ression istons, different ca's,e9cellent shoc.s and a single fire ignition This is a great ste forward and an ad'ission to the singlefireQs desirability fro' a erfor'ance as ect& 5nfort%nately the Factory is ha'str%ng by having to co' lywith e'issions controls while the after'ar.et is not& Therefore the after'ar.et is able to rod%ce better

erfor'ing hi( erfor'ance rod%cts

TI+IBN

Advance M retard

On all 'odern Harley 0avidsons, e9ce t the f%el in-ection 'odels and the !""7 34 !?>> S ort the s ar.l%g fires twice as often as is reD%ired& This d%al fire syste' is chea to rod%ce, reD%ires less arts,

red%ces e'issions fro' the e9ha%st and it wor.s o.ay& At least yo% donQt hear a lot of co' laints abo%td%al fire which s ar.s the l%gs near the to of the co' ression stro.e initiating the all i' ortant owerstro.e fro' which everything e'anates b%t also fires the s ar. l%gs with a )wasted) s ar. on thee9ha%st stro.e whose sole %r ose is s% osed to be to e9 el %nwanted gases as D%ic.ly and f%nctional

as ossible fro' the cylinder so that a fresh inta.e of airGgas can be s%c.ed in to begin all over again&

*%t if d%al fire is the standard fro' which yo%Qve learned and it is all yo% have ever e9 erienced, how canone .now the benefits en-oying a better syste' which is the single fire ignition&

:hen co' aring the sa'e ty es of ignitions s%ch as a d%al fire oints ignition with a single fire ointssyste', the latter set% is s% erior given eD%al D%ality of arts %sed&


26/30

*enefits

The benefits of the single fire which only rod%ces one s ar. er cycle near the to of the co' ressionstro.e to %t the oo' h into the ower stro.e and eli'inates the second )wasted) or ) hanto') s ar. onthe e9ha%st ortion of the cycle areJ

!& 4ess vibration beca%se the engine is going har'onio%sly forward instead of wor.ing against itself

?& *etter gas 'ileage beca%se 'ore ower is generated %sing the sa'e a'o%nt of f%el

@& 4onger engine life since the 'otor is not wor.ing against itself

C& A s'all increase in horse ower since all the co' onents wor. in the sa'e direction

#& 4onger s ar. l%g and wire life beca%se they are only %sed #> as '%ch

& Easier starting characteristics beca%se the iston on the e9ha%st stro.e is not trying to go bac.wardsand((

$& The ability to go to leaner -etting and to -et the carb%retor 'ore recisely which is an i' rove'ent on'any fronts incl%ding e'issions controls&

Bow lets %t all of this into ro er ers ective beca%se converting to single fire is not on the sa'e levelas receiving 'anna fro' Nod b%t it does rod%ce s% erior res%lts that can be felt and ga%ged altho%ghthe 'odern Evo d%al fire is 'ore than adeD%ate&

F%rther'ore yo%r stoc. syste' is not slowly beating yo%r engine to death, b%t yo%r 'ill will receive alonger lifes an with single fire as will 'any of the s% ort co' onents&

It is a s% erior syste' that costs 'ore and this is the ri'ary reason it is not %tili> efficient and b%rned all the gas on the ower stro.e, this d%al fire wasted s ar.wo%ld be no big deal e9ce t for the coil, wires and l%gs that wear o%t twice as fast beca%se of do%ble the%sage&

:ell, yo% .now what I 'ean, since not all the gas is b%rned in any engine to date&


27/30

So, the wasted s ar. is igniting resid%e oc.ets of gas on the wrong stro.e to rod%ce so'e 'inor owerthat o oses the e9ha%st stro.e iston which is being very forcef%lly driven % by the ower stro.e on theo osite cylinder which is occ%rring at the sa'e ti'e as the e9ha%st stro.e on itQs 'ating cylinder&

This is what ha ens when the d%al fire wasted s ar. ignites the resid%e gas& It creates a wave of heat

ress%re that is artially dissi ated by the o en e9ha%st valve altho%gh so'e of this energy tries to drivedown the the % wards iston, creating vibration, as this ins%rgency tries to 'a.e the engine wor. againstitself&

Bow to reiterate a very 'a-or oint when co' aring a single fire to a stoc. d%al fire syste' and that is toco' are a les to a les and oranges to oranges not a les to oranges& They are both fr%it b%t they aredifferent fr%it&

A 4evel Playing Field

Therefore we sho%ld co' are a 'echanical Harley d%al fire oints syste' with a 11I single fire ointsignition, or a Factory !"$7($" Prestolite 6(Fire I d%al fire with a 0yna SQ single fire whose advanceGretardti'ing c%rves are governed by the centrif%gal advance weights and s rings, or, finally the highly efficient6(Fire III stoc. d%al fire %sed since !"7@ with a 1rane HI(C electronic single fire ignition&

:hen co' aring on this level laying field a s'all increase in horse ower will be achieved by the singlefire syste's b%t if we tilt the laying field one way or the other the following wo%ld ha en&

For e9a' le, I can g%arantee yo% that a single fire oints syste' will ca%se a decrease in horse ower ifs%bstit%ted into a 'odern Evo %tili


28/30

ti'e& Therefore the l%g does not fire at to dead center when the ower stro.e is beginning b%tso'eti'e before on the co' ression stro.e to allow eno%gh ti'e for the gas to b%rn which generatesheat which e9 ands and ca%ses ress%re&

Advance Ti'ing

Si' le eno%gh That is %ntil different acceleration and load rinci les ta.e effect&

For e9a' le, with acceleration, the iston 'oves % and down faster in the cylinder b%t the gas is stillb%rning at the sa'e rate&

The s ar. l%g '%st ignite sooner to b%rn all the gas& This is advanced ignition ti'ing&

Retard Ti'ing

Once the bi.e has attained highway s eed in a higher gear the iston slows down relative to when thebi.e was accelerating %nder load& The s ar. l%g goes off later beca%se the iston is not 'oving as fastwhich 'eans the ti'ing is retarded&

The so histicated electronic ignitions whether they be Factory or after'ar.et all have a variety of ignitionti'ing c%rves which a ly to different riding conditions whereas the artial electronic or 'echanical ointswhich both %se centrif%gal activated weight syste's only have one c%rve which is advanced when in'otion and retarded when starting the bi.e&

S% ose we %t an electronic single fire ignition into a stoc. d%al fire oints syste' Harley& The benefitswo%ld be i''ediately noticeable and a definite horse ower increase wo%ld occ%r&

The ) oints) aficionados will robably hate 'e by now for 'aligning their favorite ignitions b%t facts arefacts&&&and besides, IQ' only %sing the' for co' arative %r oses& There are other reasons that 'anyriders refer oints over electronic(((li.e yo% can fi9 the' at the side of the road, whereas thetransistori


29/30

The 1rane coil even sits nicely and %nobtr%sively behind the stoc. coil brac.et while d%al coil set% s li.e0yna or RevTech sit in elaborate to%gh loo.ing brac.ets that let the whole world .now that yo% arer%nning a hi( erfor'ance single fire ignition syste'&

Tacho'eters can resent a roble' with so'e single fires since they will only read at half the act%al

r 's beca%se the s ar. l%gs are only firing half as often b%t there are diode .its li.e 1rane art U 7(?>#>that correct this easily and chea ly& This is %s%ally only a concern with the advance weight syste's onre(!"7> Harleys that are not electronic or totally electronic& Any of the to all electronic .its li.e 1rane,

0yna and 1o' %fire, to na'e a few, have internal diodes to correct the tacho'eter readings&

0yna %sed to be the biggest na'e with itQs 0yna SQ .it which I never ersonally %nderstood beca%se it%tili


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These .its are easily installed and reliable& IQve tort%re tested these .its and have had e9tre'ely goodres%lts altho%gh the stoc. Evo d%al fire ignition obvio%sly oses no roble's either&

0onny

a history of the sportster

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