Yamaha QT 50F User manual

1

NOTICE
ThismanualhasbeenwrittenbyYamahaMotorCompanyforuseby
AuthorizedYamahaDealersandtheirqualifiedmechanics.Inlightofthis
purposeithasbeenassumedthatcertainbasicmechanicalpreceptsand
proceduresinherenttoourproductarealreadyknownandunderstoodby
thereader.Thisservicemanualhasbeenwrittentoacquaintthemechanic
withcommondisassembly,inspection,reassembly,maintenance,and
troubleshootingproceduresassociatedwiththismachine.
TheResearch,Engineering,andServiceDepartmentofYamahaare con-
tinuallystrivingtofurtherimproveallmodelsmanufacturedbythecom-
pany.Modificationsarethereforeinevitableandsignificantchangesin
specificationsorprocedureswillbeforwardedtoallAuthorizedYamaha
Dealersand will, whereapplicable,appearinfutureeditionsofthismanual.
Particularlyimportantinformationis distinguished inthismanualbythe
followingnotations:
NOTE: A NOTEprovideskeyinformationtomakeprocedures
easierorclearer.
CAUTION: A CAUTIONindicatesspecialproceduresthatmustbe
followedtoavoiddamagetothemotorcycle.
WARNING:A WARNINGindicatesspecialproceduresthatmustbe
followedtoavoidinjurytoa motorcycleoperatororper-
soninspectingorrepairingthemotorcycle.
QT50F
SERVICEMANUAL
1stEdition-March1979
2ndPrinting,November 1980 OCL
3rdPrinting,July 1981 OCL
ALLRIGHTSRESERVEDBY
YAMAHAMOTORCORPORATION, U.S.A.
PRINTEDIN U.S.A.
LIT-11616-01-31
I
J

SECTIONINDEX
V
GENERALINFORMATION
PERIODICINSPECTIONAND
ADJUSTMENTS
ENGINEOVERHAUL
j
//
CARBURETlON
CHASSIS
ELECTRICAL
'vVys
APPENDICES
•- «*i
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MS
CHAPTER 1.GENERALINFORMATION
1-1. MACHINEIDENTIFICATION1-2
1-2.SPECIALTOOLS1-2

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CHAPTER1.GENERALINFORMATION
1-1. MACHINEIDENTIFICATION
The fr&me serialnumberislocatedonthe
frontslideoftheheadpipeassembly.The
firstthreedigitsidentifythemodel.Thisis
followedbya dash.Theremainingdigits
identify:theproductionnumberoftheunit.
POCKET TESTER'
ToolNo.90890-03096
FLYWHEELHOLDINGTOOL
Tool No.90890-01235
Theengineserialnumberislocatedona
raisedbossonthelowerleftsideofthe
engine.Engineidentificationfollowsthe
samecodeasframeidentification.
1. Engineserialnumber
ft
•J%
u$
I®.
' -a
4W
m
~
.sB
wmmB^LM
ELECTROTESTER
Tool No.90890-03021
DIALGAUGE
ToolNo. 90890-03110
FLYWHEELPULLER
ToolNo. 90890-01189
1-2

CRANKICASE SEPARATIONTOOL
Tool,No. 90890-01135
CRANK
Tool Nci
INSTALLERPOT
90890-01274
ADAPTER CRANKINSTALLERBOLT
Tool No!, 90890-01278(M12)
EXHAU >T RINGandSTEERINGNUTWRENCH
Tool No. 90890-01268
Additional ToolsandSupplies
1. Thicknessgauge set
2. Torque wrench
3.Tirepressuregauge
4. Fluidmeasuringcup
5.Micrometer
6.Verniercaliper
7.Cylindergauge
8.Magneticstand
9.
10.
11.
12.
13.
14.
15.
BOLT
ToolNo.90890-01305
CRANKINSTALLERBOLT
ToolNo.90890-01275
HEXAGONWRENCH
Toll No. 90890-01306 (25)
90890-01307(22)
Greasegun
Yamalube 4-cycle oil
Yamalube 2-cycle oil
Wheelbearinggrease
YamahabondNo.4
YamahaChainandCableLube
Lithiumbasewheelbearinggrease
(Ex. SHELL LETHINAXA)
1-3

CHAPTER2.
PERIODICINSPECTIONAND ADJUSTMENTS
2-1.
2-2.
2-3.
2-4.
2-5.
INTRODUCTION2-2
MAINTENANCEINTERVALSCHARTS2-2
A.MaintenanceIntervals2-2
B.LubricationIntervals2-3
ENGINE2-3
A.Carburetor2-3
B.AirCleaner2-4
C.AutolubePump2-4
D.EngineandTransmissionOil2-5
E.CylinderHead2-6
CHASSIS2-6
A. Brake andWheel(FrontRear)2-6
B.SteeringandSuspension2-7
ELECTRICAL2-8
A.IgnitionTiming2-8
B.SparkPlug2-8
C.Battery2-9
D.HeadlightBeamAdjustment 2-10

CHAPTER2.
PERIODICINSPECTIONANDADJUSTMENTS
2-1. INTRODUCTION
Thischapterincludesallinformationnecessarytoperformrecommended
inspectionandadjustment.Thesepreventivemaintenanceprocedures,if
followed, willinsuremorereliablevehicleoperationanda longerservice
life. Theneedforcostlyoverhaulworkwillbegreatlyreduced.Thisinfor-
mationappliesnotonlytovehiclesalreadyinservice,butalsotonew
vehiclesthatarebeingpreparedforsale.Anyservicetechnicianperform-
ingpreparationworkshouldbefamiliarwiththisentirechapter.
2-2. MAINTENANCEINTERVALSCHARTS
Thefollowingchartsshouldbeconsideredstrictlyasa guidetogeneral
maintenanceandlubricationintervals.Youmusttakeintoconsideration
thatweather,terrain,geographicallocation,anda varietyofindividual
uses. Thistimescheduleshouldbealteredtomatchindividualowners'
requirements.Forexample,ifthemotorcycleiscontinuallyoperatedinan
areaofhighhumidity,thenallpartsmustbelubricatedmuchmore fre-
quentlythatshownonthecharttoavoiddamagecausedbywatertometal
parts.
A.Mainter
cioj
Cylinderhead
Sparkplug
Airfilter
Carburetor
Autolubepurr
*Brakesystem
*Wheelsandt
*Suspensions
Fuelpetcock
•Battery
*Lights/Signal
ance Intervals
tern
/Exhaustsystem
P
(complete)
res
stem
I* Fittings/Fastehers
Remarks
Decarbonize
Inspect/Cleaningorreplaceasrequired
Wet type-Must bewashedanddampedwith
Yamalube 2-cycle OilorSAE20motoroil
Checkoperation/Fittings
Clean/Refit/Adjust
Check/Adjust/Airbleeding
Check/Adjustas required-Repair asrequired
Checkpressure/Wear/Balance/Runout
Check operation/Repair asrequired
Clean/Flushtankasrequired
Top-up/Checkspecificgravityandbreather
pipe
Checkoperation/Replaceasrequired
Tightenbeforeeachtrip and/or...
•
Initial
1
month
O
O
O
O
O
O
O
O
O
3
months
0
O
O
O
O
O
O
O
O
O
O
O
6
months
O
O
O
O
O
O
O
0
O
O
o
o
o
Unit:
km (mi)
Thereafterevery
6
months
O
0
O
O
O
3
months
O
O
o
o
o
o
1
year
O
*Indicatespre-operation checkitems.
2-2

B.LubricationIntervals
Unit:km(mi)
1 '
Item
•Transmissionoil
*Conrolandmete
cables
Throttlegrip an<j
housing
Brakelever,
Brakecamshaft
Steeringbearing
Speedometer ge
housing
Wheelbearings
Middleandfinal
gear
*Indicatespre-opera
r
s
ar
tionchec
Remarks
Replace/Warmengine
beforedraining
Applythoroughly
Applylightly
Applylightly
Applylightly
Inspectthoroughly/Pack
moderately
Inspectthoroughly/Pack
moderately
Donotover-pack
yearlyor...
Seepage5-7torepack
grease
kitems.
Type
Yamalube 4-cycle OilorSAE
10W/30 type"SE"motoroil
SAE10W/30 motoroil
Lithiumbasegrease
Lithiumbasegrease
Lithiumbasegrease
Medium-weightwheelbearing
grease
Lithiumbasegrease
Medium-weightwheelbearing
grease
Lithiumbasewheelbearinggrease
(EX. SHELLLETHINAXA)
Initial
1
month
O
3
months
Check
O
O
o
6
months
O
O
O
0
0
Check
Thereafterevery
6
months
O
O
0
1
year
O
O
2
years
2
years
O
2
years
2-3. ENGIN
A. Carburetcir
1. Pilotairscrew
Turnairadjustingscrewuntilitlightly
seats, thenbackitouttospecification.
This adjustment canbemadewith
enginestopped.
Airscrew(Turnsout):1-3/4[1-1/2]
[]:AfterengineserialNo. 3L5-702401
2. Startthe bngine andletitwarmup.
3.Throttle stop screw
Turnthrottlestopscrewinoroutto
1. Pilotairscrew 2. Throttlestopscrew
achieve
specified
Idlingspeed
mooth engineoperation
die speed. at
1,700 r/min
4. Throttlecable
a.Throttlecable2.
Loosencableadjusterlocknut(attop
ofcarburetor)andturncableadjuster
untilspecifiedfreeplayisobtained.
Retightenlocknut.
NOTE:
Thepilotair knd throttlestopscrewsare
separateadjustmentsbuttheymustbe
adjustedatthesametimetoachieve opti-
mum operating conditionatengineidle
speeds.
Freeplay: 1.0 mm(0.04in)
1. Adjuster2. Lock nut
2-3
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III
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m

b.Throttle
cable2
directioh
cable1
After engine idlespeedandthrottle
aresetcheckplayintuning
ofthrottlegrip.Theplay
should tie 2 ~ 3 mm(0.08 ~ 0.12in)
atgripflange.Loosenthelocknutand
turnthewireadjustertomakethe
necessaryadjustment.Afteradjusting,
besure io tightenthelocknutproperly.
1. Adjuster
B.AirClean
1. Remove
element
sr
theaircleanercasecapand
assembly.
2.
3.
4.
Wash the elementgently,butthorough-
ly,in solvent.
Squeezeexcesssolventoutofelement
anddry.
Poura small quantityof20W.motoroil
onto cleelner elementandworkthor-
oughlyintotheporousfoammaterial.
Element ihust bedampwithoilbutnot
dripping.
5.Re-installtheelementassembly,case
coverandseat.
NOTE:
Eachtimecleanerelementmaintenanceis
performed, checktheairinlettothecleaner
caseofobstructions.Checktheaircleaner
jointrubbertothecarburetorandmanifold
fittingsforanair-tight seal. Tightenallfit-
tingsthroughlytoavoidthepossibilityofun-
filteredairenteringtheengine.
r-CAUTION:
Neveroperatetheenginewiththeair
cleanerelementremoved.
Thiswillallow unfiltered airtoenter,
causingrapidwearandpossibleengine
damage.Additionally,operationwith-
outthecleanerelementwillaffectcar-
buretorjettingwithsubsequentpoor
performanceandpossibleengineover-
heating.
C.AutolubePump
1. Airbleeding
Tobleedtheoilpump,firstremovethe
bleedscrew.Startengineandrunat
idlingspeed.Thenpulltheoilpump
wireasmuchaspossible,andcontinue
toruntheengineuntilallairbubbles
disappearfromtheoilflowingoutfrom
thebleederhole.
Reinstallbleedscrew.
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