Batavus VA User manual

Application
ThisworkshopmanualappliestoBatavusVAandHS50
mopedwithLauraengine M 48.
Foreword
Thismanualismeantinthefirstplacetoassistthose,
whohavetomaintainandrepairthesemopeds,tocarry
outtheirworkinanexpertandtimesavingmannerand
tomakethemfamiliarwiththem.
Undoubtedlysomeproblemswillariseinpractice,which
havenotdealtwithinthismanual.
Incaseyoumightnotbeabletoovercomethem,our
ServiceDepartmentisfullyatyourdisposaltoassistyou
ineverypossibleway.
Index
Technicaldataengine
Technicaldataframe
Tools
Cylinderandcylinderhead
Piston
Clutch
Ignition
CarburettorandIntakesilencer
Reedvalve
Crankcaseandseals
Crankshaftandbearings
Dirtshield,sparkplugandfuel
Troubleshooting
Crankaxledis-andreassembly
Engineremoval
SwingarmandCenterstand
Various
Steeringlock
Frontfork
Wheels
Silencer
Electricalequipment
Electricaldiagram29/5W
Electricaldiagram 22/10/5 W
Importantnotice
OnlyoriginalBATAVUSandLAURApartsguarantee
ultimatesafetyandprotectionagainstneedlessdamage.
Warrantyclaimswillnotbeacceptedwhenassemblyor
useofimitationreplacementpartsareestablished.
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page6-7
page8-9
page 10-11
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page 16-17
page18-19
page20-21
page22-23
page24
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page26-27
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1

Technicaldataengine
TypeofengineTwostrokeengine,reedvalvecontrolled.
Borex stroke40x 38mm.
Cubiccapacity 48cc(2.9 cu.in.)
CylinderSpecialcastiron
CylinderheadAluminumalloy
CylinderbasegasketKlingerit
InletgasketsKlingerit
CrankcasegasketPaper
PistonVeryspecialalloyandshape.Oversize40.20mm.
PistonringsCast iron, 2 rings,oversize40.20mm.
GudgeonpinFloating
CrankshaftBuilduptype,ballbearingoneachside
BearingsBigendborehonedtroughwichextremelyhighaccuracy.
Connectingrod:big-endneedlebearing
little-endbronzebushing
Clutchhousing:Needlebearingwithsealononeside.
MixturePulley:Twoneedlebearingswithsealonbothsides.
Regulargas(notpremium!)anda goodqualitytwostrokeoil.
Proportionduringbreakinperiod1 :40(2,5%)thereafter 1 : 50(2%).
Execution
Compressionratio
OutputHP
Torque ftlb
Carburettortype
Throttlevalvenr.
Yetsize
Ignition
6V-22/10/5W.
Sparkplug
Gearratioprim.
Gearratiosec.
20mph.
6:1
1.2
2.0
S23A
190
52-50
validforengines
tonr.772302
6V-29/5W.
Validforengines
fromnr.772302
6V-22/10/5W.
BoschW 175 T1
Champion L85
4.1: 1
48: 11
25 mph.
7:1
1.7
2.3
S8A
190
54-52
validforengines
tonr.779301
6V-29/5W.
Validforengines
fromnr.779301
6V-22/10/5W.
BoschW 175 T1
Champion L85
3.6:1
50: 13
30mph.
8:1
2.0
2.5
S22orS 25
405167
58-56
validforengines
tonr. 780501
6V-29/5W.
Validforengines
fromnr.780501
6V-22/10/5W.
BoschW 240T1
Champion L81
3.6:1
50:13
Technicaldataframe
FrameSingletubeframewithseperatefueltank.
Positionofframenr.Rightsideofstearinghead.
FrontforkTelescopictype;5 cc.greaseRetinaxA perforkleg.
Rear forkSwingaxletype.
FueltankBatavusVA.92gal.(3.5)litres.
BatavusHS50 1.3 gal.(5litres).
LightingHeadlamp 6 V-21 W.
Brakelight6V-10W.
Tailight6V-5W.
Electichorn 6 V-24W.A.C.
TyresFrontandrear2-16".
TyrepressureFront 28 lbs.
Rear 34lbs.
RimsFrontandrear1.20x 16".
Dryweight107lbs.(48.5kg.).
Max. G.V.W. 350lbs.(160kg.).
ChainsEnginetransmission 1/2x3/16".
Pedaltransmission 1/2x1/8".
10.76

Tools
Forspecialtoolsseesparepartslist.
Metricaltoolsneeded:
Tubespanner10mm.
Tubespanner17mm.
Openendedspanner
Openendedspanner
Openendedspanner
Openendedspanner
Openendedspanner
Openendedspanner
Openendedspanner
Closeendedspanner
Closeendedspanner
Closeendedspanner
Closeendedspanner
Closeendedspanner
Closeendedspanner
8x
10x
12x
14x
16x
18x
8x
10x
12 x
14x
16x
18x
9mm
11 mm
13mm
15mm
17mm
19mm
32mm
9mm
11 mm
13mm
15mm
17mm
19mm
10.76 3

Cylinderandcylinderhead
The M 48engineisequipedwitha castironcylinder.
Acastironcylinderischeaperthananaluminumoneand
hasalsotheadvantagethatthecylinderborecanbe
rehonedafterbeingdamaged.
Asthespecificpoweroftheseenginesisrelativelylow
(abt..7hp/cu.in.)theheatabstractionissufficient.
Henceanaluminumcylinderisnotnecessary.
Inthecaseofa rehonedcylinderboreanoversizepiston
shouldbeapplied.
Inordertogettherequiredpistonclearancethediameter
oftheborehastoberehonedto40.245- 40.255mm.
Beforedismantlingthecylinder,thesurroundingsofthe
cylinderbasehavetobecleanedwitha brushand
kerosinetopreventdirtfromgettingintothecrankcase.
Removethesparkplug.
Removethe4 nutsofthecylinderstuds(takecarethat
theplainwashersandthespringwashersdonotget
lost)andthetwoboltsoftheexhaustpipe.
Removethecylinderheadandcarefullytakeoffthe
cylinder.
Removethecylinderbasegasket.
Puta notfluffyragaroundtheconnectingrodtoprevent
dirtfromgettingintothehousing.
Takecarethatthejointsurfaceswillnotbedamaged.
Beforeassemblingcylinderandcylinderheadthejoint
surfaceshavetobecleanedverycarefully(dontscratch!)
Decarbonizethecylinder(especiallytheexhaustport)
andcylinderheadifnecessary.Protectthecylinderbore
witha ragwhendecarbonizingtheexhaustportinthe
wayasshowninpict. 1.
Alwaysusea newcylinderbasegasketandneverany
seal!
Putthebasegasketintherightposition,otherwisethe
gasketwillpartlycoverthescavengingports,thus
causinglostofpower.
Sincethecylinderheadisthebestcooledpartofthe
engine,itisveryimportantthattheheatconduction
fromcylinderintothecylinderheadwillnotbedisturbed.
Thereforeneverusea gasketoranysealbetween
cylinderandcylinderhead!!
Thejointsurfacesaremachinedinsucha waythatthere
willbenoleakageatall,evenwithoutgasketor seal.
Thecylinderboreistaperedsothattheuseofa clamp
forthepistonringsisnotnecessary.
Thepistonringscanbepinchedtogetherasshownin
pict.3.
Pict.3
Besurethatthelocatingpegsinthepistonareindeed
insidetheringgaps.Beforeassemblythecylinderbore
shouldbeoiled.
Aftercarefullypushingthecylinderalongthepistonon
thecrankcase,thecylinderheadwithplainwashers,
springwashersandnutscanbeassembled.
Tightennutscrosswise!
Fitspark plug.
Pict.1
Todeterminewhetherthecylinderboreiswornouttoo
farputa newpistonringintotheboreandcheckthegap,
whichhastobebetween.2and.5mm(.008"and
.020"). Seepict.2.
Pict.2
10.76
4

Piston
Tominimizethedifferenceinexpansionbetweenpiston
andcylinderthepistonismadeofa veryspecialalloy.
Moreoverthepistonhasa veryspecificshape.
Anotheradvantageofthisspecialalloyisthatitisvery
hardsogudgeonpinboresdonotwearout.
Whendemountingpiston,firstremovepistonrings.
Whenreassemblingthepistonringsbesuretoputthe
ringsinthesamepistonringgrooveasbefore.
Thereafterremovebothcirclipswitha pairofplierswith
flatbits,andpressgudgeonpinoutofthepiston.
Beforereassemblingthepistonfirstcheckthegapofthe
pistonrings.Seepict.2.
Cleantheringgroovesinthepistoncarefullybefore
assemblingtherings.
Beforeassemblingthepiston,oneofbothcirclipshasto
beplacedinthegudgeonpinbore.Alwaysusenew
circlips.
Pushthegudgeonpinintothepistonboreinsucha way
thatthepinprotrudesinsidethepistonabout3 mm.
(.12").
Fitthepistonontheconnectingrod(firstoilthelittleend
bush)andpresstheprotrudingpartofthepinintothe
littleendbush.
Pressthepinintotherightpositionandfitthesecond
circlip.
Fitthepistonringsinpreviousgrooves.
Besurethatthearrowonthepistonbottompointsatthe
exhaustport.
10.76

Clutch
Theconstructionoftheclutchisshowninpict.4
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m
Schematictheclutchisshowninpict.5.
H
•
M
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98 10
Pict.5
Operation:
Spring1 isfilledwithsteelballs,thespringendsare
screwdtogether.
Thediameterofthespringislessthanthediameterof
theclutchhubonwhichthespringisfitted,sothat
mountingcausesa certainprestressinthespring.
Whenthecrankshaftisrevolving,alltheshadedparts
andtheclutchspringrevolvesinceallthosepartsare
attachedtothecrankshaft.
Atabout2500 rpm. thecentrifugalforceontheballsin
thespringhasbecomesufficienttoexceedthe pre-stress
forceinthespring,resultinginanoutwardmouvement
oftheballs.
Asthespringwillnowmovealongtheslopingsideofthe
clutchhub2,itwillatthesametimebeforcedtomove
totheleftside,pressingtogetherpressureplate3,clutch
plate4 andendplate5.
Inthiswaytheclutchplate(withcams)willcausethe
clutchhousing6 torotate.
Whenstartingtheenginetheprocesisreversed.Now
thestarterleafspring7 pressesallplatestogether.
Thedistancebetweenthestarterleafspringandthe
thrustpiece(xinpict.5)hastobe.5- 1 mm
<.020"-.039").
Thisdistancecanbeadjustedbybendingtheleafspring
fittedonthehousing,incasethedistanceistosmall.
Ifthedistanceistolargethestarterleafspringhastobe
removedfromtheengine.Afterputtingitina viceitcan
bebendedintocorrectpositionandrefittedagain.
Alwaysgreasethethrustpiece!
Aneedlebearing,suppliedwithanoilsealatthecrank-
casesideisfittedintheclutchhousing.
Aseperatesealisfittedintheoppositesideofthebore.
Thisisa feltringatfirstassembly.
Storingmaycausethefeltringtobecomedry.Therefore
itismuchbettertofitanoilsealinsteadofa feltring,in
caseofrepair.
Ifa newneedlebearinghastobefitteditshouldbedone
insucha waythatthemeasureijinpict.5 is25.5-
26.5mm(1.0039" -1.0079").
4
Onlypressonthemarkedsideofthecage,other-
wisetheneedlebearingwillbedamagedirreparable.
Theclutchhousingofthe20 mph. and25-30 mph.
enginesaredifferentbroadwise,becausethe V-belt and
theprimaryreductionaredifferentforthe20mph.and
25-30mph.engine.
10.76 6

Todistinguishthemveryclearlythehousingofthe
20 mph. engineispaintedyellow-brownandtheonefor
the25-30mph.engineispaintedred-brown.
Topreventtheclutchhousingandclutchhubfrom
wearing, a steelwasher15x 28x .5mm(.59x 1.1x
.020")nr. 11 inpict.4 isfittedonthecrankshaft.
Take care thatthiswasheriswellcenteredonthecrank-
shaft!!Whenfittingthiswasheritisbettertoputthe
crankshaftina verticalposition.
In frontofthissteelwashera saucerspringhasbeen
placed. Thehollowsideofthissaucerspringmustbeon
clutchside(oppositeengineside).
Thisisveryimportant!
Onlythe25-and30mph.engineshavea secondsteel
washer(12x 24x .5mm..47x .95x .020")infrontofthe
saucerspring,toassuresufficientclearancebetween
cultchhubandclutchhousing.
Replacementofoneoftheparts1 to5 pict5 hastobe
followedbycheckingthetotalclearanceoftheclutchby
meansofa feeler-gaugeasshowninpict.6.
Thisclearancehastobe between .5and.9mm(.020and
.035").
Ifthisclearanceistoosmallthecausemaybean
undulatedendplateorpressureplate,orbecauseofthe
shapeofthescrewedspringends.
The6 nutsholdingthetotalclutchpackethavetobe
loosenedbeforedismantlingtheclutch.
Securetheclutchbyplacinga screwdriverbetweentwo
ofthenuts.
Pressonclutchpackettopreventundulatedwashers
fromsnappingaway,whenremovinglastnut.
Flattenthetabwashernr.12pict.4.Usetoolnr.
48.50.05asa steadyandloosenthecentralnut.Next
takethereversesideoftool48.50.05andfitittothe
clutchhub,tightenitwith2 nuts,screwthepinofthe
littleendbushpressintothethreadedholeandpullof
thehubfromthecrankshaftasshowninpict.7.
Theclutchhousingcanbepulledoffbyhand.
Whenreassemblingtheclutchbesureoftherightorder
ofthesteelwashersandsaucerspringandtheright
positionofthesaucerspring.
Alwaystakea newtabwasherandflangethetab
washeragainstoneofthenutsides,aftertighteningthe
nut.
Betweenclutchhousingandclutchplatea leafspring
nr.13pict.4 isfittedononeoftheclutchplatecams.
Theonlypurposeofthisspringistopreventanynoise
whiletheengineisidling.
Itdoesnotinterferewiththeclutchfunction.

Ignition6 V -29/5W.
Validfor:20 mph. enginestonr.772302
25mph.enginestonr. 779301
30mph.enginestonr.780501
Theignitionissupplied with:
1Coil29W.fortheheadlight
1Coil5 W.foradditionalchargingofthe
battery
1H.T.coil
Allthesecoilsaremountedonthebaseplate,placedin
theflywheel.
Whendismountingtheflywheelitmustbesecuredby
tool nr.48.50.10.
Afterremovingthenut,theflywheelcanbepulledoff
withtoolnr.48.50.02securedagainwithtoolnr.
48.50.10.
Alwaysputtheflywheelwiththeopensideupwardson
theworkbenchtopreventironparts,likesmallwashers,
tobeattractedbythemagnetos.
Loosenthe3 screwsofthebaseplateandremovethe
baseplateoutofitspositioninthecrankcase.
Inordertomovethewiresfreelythroughtherubber
grommets,oilthema littlebefore.
Neverpullthebaseplatetomovethewiresoutofthe
grommetsbutalwayspullthewiresthemselves.
Mountingtheignitionthewireshavetobeputintothe
grommetsfirst.Someoilonthewiresmakesiteasier.
Fitthebaseplateintothecrankcaselocation,between
thecams.Takecarethatthisisdonecorrectlyandthat
nowireispinchedbetweenbaseplateandcasting.
Fitthe3 screwsbutdoenotyettightenthem.
Nextmounttheflywheelandmakesurethatthekeyfits
inthekeygrooveoftheflywheel.Fitplainwasher,
toothedwasherandnutonthecrankshaft.
Securetheflywheelagainwithtoolnr.48.50.10and
tightenthenut.
Nowturntheflywheelclockwiseuntilthebreakergapis
maximum,visiblethroughtheholesintheflywheel.
Checkthebreakergap.
Thegapmustbebetween.35and.45mm.(.014and
.018").
Ifthegapisnotcorrectitcanbeadjustedbyloosening
thescrewofthebreakerpointset,andmovingthefixed
contactintothedesireddirectionbymeansofa screw
driver.
Forthecapacityofthesparktherupturedistance(see
pict.8 distanceA)isveryimportant.
/
:
\
Pict.8
Thisdistance has to be 7-11 mm. (.28.39").
Thisisanindicationforsuchpositionoftheflywheel
wherethemagneticfieldchangesitsdirection:a position
inwhichtheelectriccurrentismaximum.
Therupturedistancecanonlybechangedbychanging
thebreakergap.
Alargerbreakergapwillgivea smallerrupturedistance,
ashorterbreakergapmeansa largerrupturedistance.
Allpartsaremachinedinsuchanaccuratewaythatthis
rupturedistanceisautomaticallyiscorrectwhenthe
breakerpointgapiscorrectlyadjusted.
Theproceedingsmentionedbeforeguaranteemaximum
spark.
Nowtakecaretohavethismaximumsparkattheright
positionofthepistoninthecylinder,whichis1.8-
2.2. mm. (.071" - .087")before T.D.C.
Toadjustthis,screwa dialgaugeintothesparkplughole
ofthecylinderhead.
TurntheflywheelclockwiseuntilpistonisatT.D.C,
whichisthepointwherethedialpointerchangesits
direction.
Nowconnectanignitionadjustingapparatus,onewire
grounded(forinstanceoncylinderhead)theotheroneto
thecut-offwire ofrthe ignition(blackwire).
Aslongasthebreakerpointsareclosedthelampofthe
adjusterwillburn.
Turntheflywheelanti-clockwise.Themomentthe
breaker pointsopenthelampwillextinguishbecauseof
theinteruptionoftheelectriccircuit.
Watchthedialgaugetoseehowfarthepistonhas
descended.
Whenthelatterislessthan1.8mm. (.071") thespark
betweenthesparkplugelectrodesistoolateorinother
wordstheignitionisretarded.
Inthatcasethebaseplatehastobeturnedanticlock-
wise.
Whenthedescendingofthepistoninthecylinderatthe
momentofignition,ismorethan2.2mm. (.087") the
sparkistooearly,orinotherwordstheignitionis
advanced. Inthatcaseturnthebaseplateclockwise.
Thushavingadjustedthemomentofignition,thethree
baseplatescrewscanbetightened.
Insteadofusinga dialgaugea slidinggauge(vernier
calipers)canbeusedasfollows:
TurnthepistoninT.D.C.andmeasurethedistance
betweenpistonbottomanduppersideofthesparkplug
hole.
Turnbacktheflywheeltillthelampextinguishand
measurethedistanceagain.
Thedifferencebetweenbothsizesistheignition
advance.Ifoneonthecoilshastobereplacedusea
feelergaugetochecktheairgapbetweeninnerrim
(magnetos)andcoreshoes.
Thisgaphastobe.2mm.(.0079").Seepict.9.
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i
limn i
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Pict.9
10.76 8

Ignition 6 V-22/10/5 W.
Validfor:20 mph. enginesfromnr.772302
25mph.enginesfromnr.779301
30mph.enginesfromnr.780501
Theignitionissupplied with:
1coil22W.fortheheadlight.
1coil10W.forthebrakelight.
1coil5 W.fortherearlight.
1coilasa primaryignition coil.
Allthesecoilsarefittedonthebaseplate,placedinthe
flywheel.
TheH.T.coilismountedoutsidetheflywheel.
Thismeansanimportantimprovementcomparedwith
theformerconstruction,becausetheexternalcoilcanbe
dimensionedmuchlargerandkeptmuchcooler.
BurningoutoftheH.T.coilisnowpracticallyimpossible.
Demounting,mountingandadjustingofthisignitionis
exactlythesameasforthe6 V.- 29/5W.ignition.
Theonlydifferenceisthatforthe6 V.- 22/10/5W.
ingnitiontherupturedistanceis20- 25mm. (.79".98")
andthecut-offwireistheblueone.
10.76 9

Carburettor
The20 mph. engineissuppliedwitha carburettortypeS
23A,diameter8 mm. (.32") jet52- 50,Throttlevalve
nr. 190.
The 25mph.engineissuppliedwitha carburettortypeS
8A,diameter8 mm. (.32") jet54- 52,Throttlevalve
nr. 190.
The30mph.engineissuppliedwitha carburettortypeS
22diameter12mm. (.47") jet58- 56,Throttlevalve
nr.405.
Recently(October1976)the30mph.engineissupplied
witha carburettortypeS 25,diameter12mm. (.47")
jet58- 56,Throttlevalvenr.167.
Demounting:
Thecarburettorisfixedontheinductionpipebya
clampingscrew.
Firstremovetheintakesilencerbydetachingthesilencer
clip.
Loosenthescrewtop(nr.85pict.10)ofthethrottle
valvehousingandtakethethrottlevalvenr.81outofthe
housing.
Unhookthechokecablefromthechokevalvenr.95,pull
offthefuellinefromthebanjonr.101andafter
looseningtheclampingscrewthecarburettorcanbe
pulledofffromtheintakepipe.
Thejetholdernr.87withjetnr.82isfittedinthe
housing.
Thejetholdercanbescrewedoutofthecarburettor
housingwitha scrwedriver.
Inthesamewaythejetcanbescrewedoutofitsholder.
Anewengineisalwaysequipedwiththelargestofthe
twomentionedjets.
Afterthebreakinperiodthisjetunsuallymustbe
replacedbythesmallerjet.
Ina fewcasesthisjetmaybetoosmall,thusgivinga
mixturebeingtoopoor.
Thiscanbedeterminedeasilyasfollows:
Ridethebikewithfullyopenedgasgrip.Afterthebike
hasreachedmaximumspeedandtheengineison
workingtemperaturethegasgripmustbepartlyclosed
(abt.30%).
Inthebikeisapttoridefasteritisevidentthatthejetis
toosmall.
Inthatcasethelargerjetmustbefittedagain.
Incaseofa dirtyjetnevertrytocleanitwitha wireora
needle,alwayscleanitbyblowingairtroughthejet!
Theatomiserisfittedonthebottomofthethrottlevalve
housing.
Thisatomiserispressedintothecastingona precise
level, andcannotbereplaced.Bytheway,thiswill
neverbenecessary.
Thethrottlevalvenr.81hasa guideinthehousing,soit
cannotbemountedfaultly.
Itmayhappen,causedbya damage,thatthevalvecan
notmovefreelyinsidethehousing.Inthatcasethevalve
mustbeburnishedwihtpolishingpaper.
Thelevelinthefloatchamberisregulatedbya plastic
floatnr.97.
VER&KPL
CARB CPL.72
1
Pict.10
10.76
10

Occasionallythisfloatmaybeleak.Thiscanbechecked
clearlybyholdingituptothelight,a leakingfloatshows
themixtureinside.
Whenassemblingthefloattakecarethatthefloatneedle
joinstheguideinthebottomofthefloatchamberaswell
astheguideinthecover.
Thiscanbecheckedeaselybyshakingthecarburettor
aftermountingthefloatchambercover(screwsnotyet
tightened).
Thefloatoperatesproperlyifonehearsitmovingupand
down.
Makesurethatthepointedendofthefloatneedleisin
anupwardposition.
Theidlingspeedoftheenginecanbeadjustedbymeans
oftheadjustingscrewnr.89.Turningthescrew clock-
wisewillincreasetheidlingspeed,turningthescrew
anticlockwisewilldecreaseit(Throttlevalvemovesupor
down).
Takecarethatthegascablehastherightlength,making
surethatthethrottlevalvecandescendtothebottomof
thechamberindeed.
Thecarburettoralsohasa chokevalvenr.95.Pullingthe
chokewillcut-offtheairsupplynearly,thusprovidingan
additionalrichmixturefortheengine.
Alsothechokecablemusthavetherightlengthenabling
afullopenintakediameter.
Thebanjoboltnr.103issuppliedwitha littlefuelstrainer
nr.102.
Duetothefactthatthetapinthefueltankisalso
suppliedwitha strainer,itveryseldomhappensthatthe
banjostrainerisstoppedup.
Intakesilencer
The20and25 mph. engineshavesimilarsilencers.Both
aresuppliedwithanintaketubediameter14mm.(.55").
The30mph.enginesaresuppliedwitha tubediameter
16mm.(.63").
Thefilterofthesilencermustbecleanedingasevery
500milesandmoistenedwithoilafterwards.
Afterfittingthesilencerdonotforgettoapplytherubber
sealonthejunctioncarburettor-silencer.
Neverridea mopedwithoutanintaketubeorwith
shortenedintaketube.
Bydoingsothepoweroftheenginewillnotincrease,
theonlyresultisthatdirtwillbesuckedintotheengine,
causingseriousenginetroubles!
Thisisalsothecaseafterdrillingholesintotheintake
silencer!!
10.76

Reedvalve
Ofallpossibilitiestocontrola two-strokeengine,reed
valvecontrolassuresthebestcylinderfillingespeciallyin
thelowerrevolutionrange.
Forthatreasontheperformanceatlowrevolutionsis
betterthanwithanyothersystem,whichisvery
importantforaccelerationandclimbingpower.
Anotheradvantageisthatthisarrangementeliminates
thewasteoffuelwhichcanoccurinenginesusingother
methodsofintakecontrol.
Importantisthatthereedvalvehasbeenmanufactured
withveryhighaccuracy.
Thereedvalveisactivatedbyvariationsinpressurein
thecrancase.
Ifthepistonascendsthecrankcasevolumewillincrease
causingdecreaseofpressure(belowtheatmosferica)
whichwillopenthereeds.
Ifthepistondescendsthereverseoccurs.
Itwillbeclearthatitisextremelyimportantthatthe
reedsshutoffthereedvalvecompletely,notrequiring
anytension,sothattheycanfollowthepressure
variationsfreely.
Nevertrytochecktheelasticqualityofthereedswitha
knifeoranythinglikeit,norcleanthemwithanyother
object.
Theonlyrightwaytocleanthemiswitha softbrush
dippedinkerosine.
Incaseofanydoubtabouttheconditionofa reedvalve
(forinstancewhenseeinglightbetweenreedsand
housing),putthepointedsideofthereedvalveinyour
mouthandtrytobreatheviathereedvalve.
Ifinhalingiseasyandexhalingimpossible,thereedvalve
isstillina goodcondition.
Alwaysusea newgasketwhenmountingthereedvalve.
10.76

Crankcase
Thecrankcaseconsistoftwopartsconnectedand
tightenedwith6 screwsofequallenghtanddiameter,
andfixedtoeachotherbytwodowelpins.
Becauseofthefactthatthetwopartshavebeen
machinedconnectedtogether,replacementofoneof
thepartsisnotpossible.
Whentheenginecomestoworkingtemperaturethe
aluminumhousingwillexpandmorethanthesteelcrank-
shaftbearingsfittedinthecrankcase.Toprevent
rotatingofthebearingsinthehousing,thediameterof
thecrankcaseboresissmallerthantheoutsidediameter
oftheball bearings.-
Beforedemountingthecrankcase,loosenandremove
the6 screws.Topreventthecrankcaseboresfrom
inrreparabledamageitisnecessarytoheatthehousing
partsuptoabout 100°C (212°F)bymeansofa Bunsen
burnerora hotplateof2000W.
Aneasywaytocheckthetemperatureistospitonthe
housing. Immediateevaporationmeansthehousinghas
reachedtherighttemperature.
Seizethehousingattwocylinderstudsofthesame
crankcasehalf,usinga ragorgloves,andseparateboth
partsbytappingallaroundtheoutsideofthehousing,
usinga plastichammer.
Neverhammeronthecrankshaft!!
Beforeassemblingthecrankcasethepartsalsohaveto
beheateduptoabout100°C(212°F).
Startwiththatpartinwhichthedowelpinsarefittedto
assurea correctpositionofthegasket.Beforefittingthe
gasketthejointsurfaceshouldbeoiled.
Nextinsertthecrankshaft,clutchsidefirst,intothe
crankcase.Heattheotherpartandjoinbothparts.
Thenfitthe6 housingscrews.Afterbeingtightenedthis
operationhastoberepeatedwhenthecrankcasehas
cooleddownsufficiently.
Oilseals
Oncea housinghasbeendismantleditisrecommen-
dable tofitnewoilseals.
In c|se ofleakagethismustbedone.
How^o finda leakoilseal?:
PutthepistoninT.D.C.tobesurethatallportsofthe
cylinderareclosed.
Pullofthecarburettorfromtheinductionpipe.
Aleaknowcanbedeterminedbyblowingsmokeinto
theinductionpipe.
Whenfittingtheoilsealsalswaysusetoolnr. 48.50.11
respectivelynr.48.50.12togetherwihttoolnr.48.50.01
topreventanydamageoftheoilsealsandtobesurethat
thesealsareinthecorrectposition.
10.76

Crankshaft
Thecrankshafthasbeenmachinedwiththehighest
possibleaccuracy.
Toobtainthisoptimalaccuracyandinherentminimal
clearances,veryspecialmachinesandmeasuringtools
areneeded.
Ina verysporadiccaseofa neededreplacementofthe
connectingrod,wethereforestronglyrecommend
replacementofa completecrankshaft.
Otherwisetheaccuracycannotbeassured.
Thelittleendbushintheconnectingrodismadeoutof
bronze.
Thisbushcanbereplaced,ifnecessary,bya newoneas
follows:Pressthebushoutoftheconnectingrodwith
toolnr.48.50.03asshowninpict.11.
•
Pict. 11
Pressa newbushintotheconnectingrodwiththesame
toolasshowninpict.12.
Nowtheoilholeshavetobedrilledafterwhichthebore
ofthebushhastobereamedtoa diameter
,. + .016
12mm.
+.020
-*
Pict.12
Ifmeasuringtoolstocheckthisdiameterarenot
available,thereamingoperationshastobedoneinsuch
awaythatthegudgeonpinfitsintheborefreely
(Floating).
Theclearancehastobe.020mm.(.00079).
Besurethattheboreofthisbushissquaretothe
connectingrod.
In caseofa neededreplacementofthecrankshaftball
bearings,thesebearingsfirsthavetobeextractedwith
toolnr.48.50.09showninpict.13.
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•,-•'-
i,.-•-.,r
<
Pict.13
Protectthreadonmagnetosidewithtoolnr.48.50.07.
Whenpressingnewballbearingsonthecrankshafttool
nr.48.50.08hastobeplacedbetweenthewebbsofthe
crankshaft.Thissupportplatemustbelaidonthebitsof
avice(seepict.14)sothatnoexternalforceswillacton
thecrankshaft.
Bynotdoingsothecrankshaftwillbeirreparable
damaged.
Puta newballbearingontheshaftandfitinitsright
locationbyusinga dollynr.48.50.01seepict.14.
Pict.14
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5
^
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T
10.76 14

Dirtshield
Thedirtshield,attachedtothecrankcaseoffers
additionalprotectionagainstdirt.Neverridethemoped
withoutthisshield.
Toprotectthedirtshieldagainstdestructionspecial
distancebushesarefittedintheboltholes.Donotforget
tofitthesebushes.
Sparkplug
Thesparkplugisoneofthemostimportantpartsofthe
engine.Twotemperaturesareveryimportantforthe
spark plug:
—Thetemperatureatwhichthesparkplugburnsitself
clean.
Thistemperatureisabout 500°C (930°F).
—Thetemperaturecausingspontaneousignition.
Thistemperatureisabout900°C (1650°F).
Itwillbeclearthatthetemperaturefirstmentioned
alwaysmustbereachedtogivea cleansparkplugand
thatthesecondtemperaturenevermaybereachedto
preventdamageofforinstancethepiston.
Forthatreasonthesparkplughasa veryspecificheat
grade, whichhasbeendeterminedexperimentallyforthe
engine.
Thesparkplugforthe20and25 mph. enginesisfixedon
Bosch W 175T1withChampionL 85asanequivalent,
andforthe30mph.enginesBoschW 240T1with
ChampionL 81asanequivalent.
Thesparkpluggaphastobe.5mm.(.020").
Alwayscheckthisbecausetherearesimilarsparkplugs
witha gapof.7mm.(.028").
Alwaysusetheprescribedsparkplugtoprevent
difficulties.
Thesightofthesparkpluggivesmuchinformation
abouttheconditionoftheengine.
—Iftheelectodesaregrey/yellow-brown,theengineis
ina goodcondition.
Theheatgradeofthesparkplugiscorrect.
—A velvetlikedullblackfur
Ontheelectrodescanbecausedby:
atoolargejet
atoolargeelectrodesgap
aheatgradeto high, soa sparkplugofa toocold
type.
— A greasyblackoilyfurontheelectrodescanbe
causedby:
toomuchoilinmixture
wornoutcylinderorpistonrings
—Electrodesburntwithmeltingpearlsontheinsulator
bottomanda furconsistingofleadcompoundscan
becausedby:
atoosmalljet
aleakysparkplugora nottightenedsparkplug
heatgradetoolow,soa plugofa toowarmtype.
—Glassysandpearlsbetweentheelectrodescanbe
causedby:
adirtyairfilter
ridingwithoutorwitha shortenedintaketube
ridingwithoutdirtshield.
Fuel
Duringthebreakinperiod(500miles)themixturemust
be1 : 40(2.5%)thatmeans1 partofoilto40partsof
gasoline.
Afterthebreakinperiodthemixturecanbereducedto
1: 50(2%).
Sincetheoilinthemixtureistheonlylubricationforall
movingpartsoftheengineneverusea lowerpercentage
ofoilthanthepercentageprescribed.
Onlyusea goodquailty2-strokeoilandregulargasoline,
soneverpremium!!
10.76
15

Troubleshooting
Localizingdefectsshouldalwaysbedonesystematically.
In casetheenginewillnotstartthecutoffwirehastobe
disconnectedfirst,becauseithappensthatthiswire,
owingtodamage,contactsground.
Thereaftercheckwhetherfuelcomesintothecarburet-
tor,bypullingoffthefuellineofthecarburettor.
Ifthereisnofueljusttakeoffthefueltankcapbecause
thedesaerationmaybestoppedup,causingtoolittle
pressureonthefuelinthetank.
Troublecanbelocatedinmostofthecaseswiththedata
mentionedbelow:
I Enginedoesnotstartorbadstarting.
a-Shortcircuiting
b-nofuel
c-Noora tooweaksparkCheckasshowninpict.15
below.
Pict.15
Distancebetweenarrowsmust be 3-4mm. (.12-.16")
d-Miscellaneous
Disconnectcutoffwirefromconnectingblock.
—Desaerationoffueltankcapisstoppedup.
—Straineroffueltankcapisstoppedup.
—Fuellineispinched.
—Floatgetsstuckcausedbybendedneedleorthe
guideinbottomoffloatchamberispolluted.
—Strainerofbanjoboltisstoppedup.
—Dirtinjet.
—Sparkplugwornout.
—Pluggaptoo larg.
—Greasysparkplugcausedbytoomuch fuel, asa
resultof:— leakyfloat
—floatneedledoesnotshut
—airfilterstoppedup
—chokevalvepartlyclosed.
—Breakergapnotcorrect.(Rupturedistance.)
—Breakerpointsburnt.Replace!!
—H.T.coildamaged,nospark.Replace coil.
—FaultyconnectionofH.T.leadinH.T.coverorH.T.
coil.
—Faultycondensor.
—Faultyreedvalve
—Leakyoilsealsand/orgaskets
—Slipping V-belt
—Wornoutclutchplate
—Throttlevalvedoesnotreachthebottomofthe
throttlevalvehousing
—Exhaustsilencerorexhaustportincylindercar-
bonized.
IIEnginestartswellbutstopsaftera shorttime.IVBadtractivepowerandtoohighspeed.
—Desaerationinfueltankcapstoppedup.
—Faultycoilinsulation.
—Fuelsupplypartlystoppedup.
IllIdlingspeedremainstoohigh,inspiteof
adjustment.
—Leakysealsand/orgaskets.
—Throttlevalvedoesnotreachthebottomofthe
throttlevalvechamber.
—Toosmalljetorjetpartlystoppedup.
—Leakyoilsealsand/orgaskets.
VClutchdoesnotdisengageatidlingspeed.
Blisteringoftheclutchplatecausedbyexcessive
heating. Thisismostlytheresultofbadhandling,for
instancecontinualopeningthegasgripwithfully
drawnrearbreak.
Bydoingsoalltheenginepowerwillbeconverted
intotheclutch.
Maximum thick/iess clutchplate3.6mm.
—Undulated pressure-plate and/orendplate.
—Deformedclutchhubbywhichpressureplate and/or
endplatecannotmove.
—Faultyneediybearinginclutchhousing.
10.76 16

VICrankshaftdoesnotrotatewhenpedallingwith
pulledstartinghandle.
—Slipping V-belt
—Bendedstarterleafspring
—Wornclutchplate.
VIIBadorjerkyaccelerationofthemoped.
—Clutchclearancetoosmallcausedbyblisterson
clutchplate
—Undulatedpressureplateand/orendplate
VIIAttopspeedtoomanyvibrationsasa resultof
socalledfour-stroking.
—Toolargejet
—Stoppedupairfilter
—Partlyclosedchokevalve.
IXBadaccelerationandbadclimbingpower.
—carbonizedexhaustsilencer
—carbonizedexhaustportincylinder.
XStartingtheengineisimpossiblebecausecrank-
shaftwillnotrotate.
seizedpistoncausedby:toolitteloilinthemixture
toosmalljet
dirtincylinderasa resultof
ridingwithoutintaketubeor
withshortenedintaketube
dirtyairfilter
ridingwithoutdirtshield
—Toosmallpistonclearance
—Bendingofthepistonrod.
10.76

Crankaxledis-andreassembly
Chain:
Removepedaltransmissionchainbylooseningthe
connector.
Leftsidecrank:
Removecotterpinnutanddriveoutthepinwhile
supportingthecrank(seepict.16).
Pict.16
Crankaxleandpulley:
FirstremovebushingB andretainingwasherC andnext
thecrankaxlebyturningandpullingatthesametime.
Keeppulleysupportedwhenremovingaxletoavoid
damages(seepict.17).
Thesprocketattachedtothepulley(seepict.18itemA)
issecuredbya locknut(seepict.18itemB)withright
handthread.
Pict.17
Pict.18
The2 pulleyneedlebearingsarepressedontothepulley.
Removethepulleyevery500milescleanthebearings
andprovidethemwithsomenewgrease.
Usea persussionstamp(drift)ora smallhomemade
press(seepict.18itemC)fordis-andreassembly.
Whenpressingtheneedlebearingintoitspositionalso
seetoit,thatthepressurecomestothatsideofthe
bearingthatbearsaninscription.
Beforeremountingthepulley,cleanthebearingwith
petrolandputnewgreaseintoit.
Startreassemblingwithfittingtheretainingwasher
(1mm)totheaxleandfitpulleytemporarilywithatleast
onewasherEbetweenpedalchainwheelandpedalshaft
bearing. Takea straightruleandputitalongthe
crankcase-faceoftheengine.
Thedistancebetweenthecrankcase-faceandthepulley
onthespotsA andB (seepict.19)shouldbeexactlythe
same, viz8-10mm (.31"-.39").
^
Pict.19
Iftheyarenotthesame,theengineshouldbemoved
intoa perfectalignmentbypartlylooseningthe4 bolts
bymeansofwhichtheenginebracketisattachedtothe
frame.
Fitthe V-belt andcheckalignmentbylookingdownon
theV-belt.
10.76 18

Ifnotproperlyaligned,correctbyfittinga 0,5or1,0mm
spacerbetweenpulleyandaxlebearingatlocationE
(seepict.17).
TheV-beltcanbetensionedbypartlylooseningthe
enginefasteningboltsandcompletelylooseningthe
exhaustmufflerclamp.
Afterhafingdoneso,theV-beltcanbetensionedby
meansofthetensionadjustmentbolt(seepict.20).
Pict.20
Toremountthelefthandcrankfirstslideretaining
washer(1mm,seepict.17itemC)andbushing(see
pict. 17 itemB).FitasmanywashersC asnecessaryto
achieveanaxialclearenceofthepulleywhichnot
exceeds0,5mm(.020").
TheV-belthastherighttensionwhenitcanbe
depressed0,5cm (.020") bylightfingerpressing(see
pict.20A).
/
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Pict. 20A
10.76

Engineremoval
Inordertoremovetheengineoutoftheframe,the
followingpartshavetoberemovedfirst:
Engineshield:
Loosenthe4 fasteningscrews,liftthefrontendofthe
shieldandremoveit.
Chain:
Removeenginetransmissionchainbyreleasingthe
connector.
Intakesilencerandairfilter:
Removeintakesilencerhousingandairfilter.
4J
»
©
B
Pict.21
^
Pict.22
Seetoit,thattherubbergasketsA andB areproperly
fittedagainwhenhousingandfilterarere-assembled
(seepict.21).
Exhaustsystem:
Removeexhaustpipefromcylinderandexhaustmuffler
fromframe.
Carburettor:
Removecarburettorfromintakepipe,thenmove
carburettordownwardssothatthethrottle,chokecable
andthefuellinecanberemoved.
Thechokecablecanberemovedbyunhookingthe
connectingspring(seepict.22).
Enginecover:
Removecover;turnadjustingscrewofstartcabletoits
extremeslackpositionandremovestartcablefrom
starterleafspring(seepict.23).
^-7
V**
\
ft
1
.
Pict.23
Wiring:
Removetheplugs,connectingtheenginetothe
contacterand H.T.-coil (seepict.24).
Enginesupportsystem:
Theengineisattachedtotheframebymeansofan
enginesupport-bracket(seepict.25)inrubber
mountings.
>
A
Pict.24
10.76
X
20