Yamaha YZ450F(Y) User manual

2009
PRINTED IN JAPAN
2008.05-2.4×1 CR
(E,F,G)
34P-28199-80
YZ450F(Y)
OWNER’S SERVICE MANUAL
MANUEL D’ATELIER DU
PROPRIETAIRE
FAHRER- UND
WARTUNGSHANDBUCH
YZ450F(Y)
PRINTED ON RECYCLED PAPER YAMAHA MOTOR CO., LTD.
2500 SHINGAI IWATA SHIZUOKA JAPAN
2009
Il convient de lire attentivement ce manuel avant la première utilisation du véhicule.
Read this manual carefully before operating this vehicle.
Bitte lesen Sie diese Bedienungsanleitung sorgfältig durch, bevor Sie das Fahrzeug in Betrieb nehmen.

Read this manual carefully before operating this vehicle. This manual should stay with this vehicle if it is sold.
Il convient de lire attentivement ce manuel avant la première utilisation du véhicule. Le manuel doit être remis
avec le véhicule en cas de vente de ce dernier.
Bitte lesen Sie diese Bedienungsanleitung sorgfältig durch, bevor Sie das Fahrzeug in Betrieb nehmen. Diese
Bedienungsanleitung muss, wenn das Fahrzeug verkauft wird, beim Fahrzeug verbleiben.

YZ450F(Y)YZ450F(Y)
20092009
34P-28199-80-E034P-28199-80-E0
OWNER’S SERVICE MANUALOWNER’S SERVICE MANUAL
Read this manual carefully before operating this vehicle.Read this manual carefully before operating this vehicle.

YZ450F(Y)
OWNER'SSERVICEMANUAL
©2008byYamaha Motor Co., Ltd.
1stEdition,May 2008
Allrightsreserved. Any reprinting or
unauthorizedusewithout the written
permissionofYamaha Motor Co., Ltd.
isexpresslyprohibited.
PrintedinJapan

FOREWORD
INTRODUCTION
Congratulationsonyour purchase of
aYamahaYZ series. This model is
theculmination of Yamaha's vast ex-
perienceintheproduction of paceset-
tingracingmachines. It represents
thehighestgrade of craftsmanship
andreliability that have made Yama-
haaleader.
Thismanualexplains operation, in-
spection,basicmaintenanceand tun-
ingofyour machine. If you have any
questionsaboutthis manual or your
machine,pleasecontact your Yama-
hadealer.
Yamahacontinuallyseeks advance-
mentsinproduct design and quality.
Therefore,whilethismanualcontains
themostcurrent product information
availableatthe timeof printing, there
maybeminordiscrepancies between
yourmachineand this manual.If you
haveanyquestions concerning this
manual,pleaseconsultyour Yamaha
dealer.
PLEASEREADTHIS MANUAL
CAREFULLYANDCOMPLETELY
BEFOREOPERATINGTHIS MA-
CHINE.DONOT ATTEMPT TO OP-
ERATETHISMACHINEUNTIL YOU
HAVEATTAINEDA SATISFACTO-
RYKNOWLEDGEOF ITS CON-
TROLSANDOPERATING
FEATURESANDUNTILYOU HAVE
BEENTRAINEDIN SAFE AND
PROPERRIDINGTECHNIQUES.
REGULARINSPECTIONSAND
CAREFULMAINTENANCE,
ALONGWITHGOOD RIDING
SKILLS,WILLENSURE THATYO U
SAFETYENJOYTHE CAPABILI-
TIESANDTHE RELIABILITY OF
THISMACHINE.
IMPORTANTMANUAL
INFORMATION
Particularlyimportantinformation is
distinguishedinthis manual by the
followingnotations.
Thisisthesafety alert symbol. It is
usedtoalert you to potential per-
sonalinjuryhazards.Obey all safe-
tymessagesthat follow this
symboltoavoid possible injury or
death.
AWARNINGindicatesa hazardous
situationwhich,if not avoided,
couldresultin death or serious in-
jury.
ANOTICEindicates special pre-
cautionsthatmust be taken to
avoiddamagetothe vehicle or oth-
erproperty.
ATIPprovides key information to
makeprocedureseasier or clearer.
SAFETYINFORMATION
THISMACHINEIS DESIGNED
STRICTLYFORCOMPETITION
USE,ONLYON A CLOSED
COURSE.Itisillegal for this machine
tobeoperated on any public street,
road,orhighway. Off-road use on
publiclandsmay also be illegal.
Pleasechecklocalregulationsbefore
riding.
•THIS MACHINE IS TO BE OPER-
ATEDBYAN EXPERIENCED RID-
ERONLY.
Donotattempt to operate this ma-
chineatmaximum power until you
aretotallyfamiliarwith its character-
istics.
•THIS MACHINE IS DESIGNED TO
BERIDDENBY THE OPERATOR
ONLY.
Donotcarry passe ngers on this
machine.
•ALWAYS WEAR PROTECTIVE
APPAREL.
Whenoperatingthis machine, al-
wayswearanapp roved helmet with
gogglesora face shield. Alsowear
heavyboots,gloves,and protective
clothing.Alwayswear proper fitting
clothingthatwill not be caught in
anyofthe moving parts or controls
ofthemachin e.
•ALWAYS MAINTAIN YOUR MA-
CHINEINPROPER WORKING
ORDER.
Forsafetyand reliability, the ma-
chinemustbeproperly maintained.
Alwaysperformthe pre-operation
checksindicatedin this manual.
Correctingamechanical problem
beforeyouride may prevent an ac-
cident.
•GASOLINE IS HIGHLY FLAMMA-
BLE.
Alwaysturnoff the engine while re-
fueling.Takecare to not spill any
gasolineonthe engine or exhaust
system.Neverrefu el in the vicinity
ofanopen flame, or while smoking.
•GASOLINE CAN CAUSE INJURY.
Ifyoushould swallow some gaso-
line,inhaleexcessgasoline vapors,
orallowany gasoline to get into
youreyes,contacta doctor immedi-
ately.Ifany gasoline spills onto
yourskinor clothing, immediately
washskinareas with soap and wa-
ter,andchange your clothes.
•ONLY OPERATE THE MACHINE
INANAREA WITH ADEQUATE
VENTILATION.
Neverstartthe engine or let it run
foranylengthof time in anenclosed
area.Exhaustfumes are poison-
ous.Thesefume s contain carbon
monoxide,whichby itself is odor-
lessandcolorless. Carbon monox-
ideisa dangerous gas which can
causeunconsciousnessor can be
lethal.
•PARK THE MACHINE CAREFUL-
LY;TURNOFF THE ENGINE.
Alwaysturnoffthe engine if you are
goingtoleave the machine. Do not
parkthemachine on aslope or soft
groundasit may fall over.
•THE ENGINE, EXHAUST PIPE,
MUFFLER,ANDOIL TANK WILL
BEVERYHOT AFTER THE EN-
GINEHASBEEN RUN.
Becarefulnot to touch them or to
allowanyclothing item to contact
themduringinspection or repair.
•PROPERLY SECURE THE MA-
CHINEBEFORETRANSPORTING
IT.
Whentransportingthe machine in
anothervehicle,alwaysbe sure it is
properlysecuredand in an upright
positionandthat the fuel cock is in
the"OFF"position. Otherwise, fuel
mayleakout of the carburetor or
fueltank.
F.I.M.MACHINE WEIGHTS
Weightsofmachines without fuel
Theminimumweight s for motocross
machinesare:
fortheclass 125 cc:
minimum88kg (194 l b)
fortheclass 250 cc:
minimum98kg (216 l b)
fortheclass 500 cc:
minimum102kg (225 lb)
Inmodifyingyour machine (e.g., for
weightreduction),take note of the
abovelimitsof weight.

HOWTOUSE THIS MANUAL
FINDINGTHEREQUIRED PAGE
1. This manual consistsof seven
chapters;"GeneralInformation",
"Specifications","Regularinspec-
tionandadjus tments", "Engine",
"Chassis","Electrical"and "Tun-
ing"
2. The table of contents is at the be-
ginningofthe manual. Look over
thegenerallayout of the book be-
forefindingthen requiredchapter
anditem.
Bendthebook at its edge, as
shown,tofind the required fore
edgesymbolmark and go to a
pageforrequired item and de-
scription.
MANUALFORMAT
Allofthe procedures in this manual
areorganizedin a sequential, step-
by-stepformat.The information has
beencompliedto provide the me-
chanicwithan easy to read, handy
referencethatcontains comprehen-
siveexplanations of all disassembly,
repair,assembly,and inspection op-
erations.
Inthisrevisedformat, the condition of
afaultycomponent will precede an
arrowsymboland the course of ac-
tionrequiredwill follow the symbol,
e.g.,
•Bearings
Pitting/damage→Replace.

HOWTOREAD DESCRIPTIONS
Tohelpidentify parts and clarify pro-
ceduresteps,there areexploded dia-
gramsatthe start of each removal
anddisassemblysection.
1. An easy-to-see exploded diagram
"1"isprovided for removal and
disassemblyjobs.
2. Numbers "2" are givenin the or-
derofthe jobs in the exploded di-
agram.Anumberthat is enclosed
byacircle indicates a disassem-
blystep.
3. An explanation of jobsand notes
ispresentedin an easy-to-read
waybythe use of symbol marks
"3".Themeanings of the symbol
marksaregivenon the next page.
4. A job instruction chart "4" accom-
paniestheexploded diagram,
providingtheorder of jobs, names
ofparts,notes in jobs, etc.
5. For jobs requiring more informa-
tion,thestep-by-step format sup-
plements"5"are given in additi on
totheexploded diagram and job
instructionchart.
ILLUSTRATEDSYMBOLS(Referto
theillustration) Illustratedsymbols"1"to "7" are used
toidentifythe specifications appear-
inginthe text.
1. Withenginemounted
2. Fillingfluid
3. Lubricant
4. Specialtool
5. Tightening
6. Specifiedvalue,Service limit
7. Resistance(Ω),Voltage (V),
Electriccurrent(A)
Illustratedsymbols"8" to "13" in the
explodeddiagramsindicate grade of
lubricantandlocation of lubrication
point.
8. Applyengineoil
9. Applymolybdenumdisulfide oil
10. Apply brake fluid
11. Apply lightweight lithium-soap
basegrease
12. Apply molybdenum disulfide
grease
13. Apply silicone grease
Illustratedsymbols"14"to "15" in the
explodeddiagramsindicatewhere to
applyalockingagent and where to in-
stallnewparts.
14. Apply locking agent (LOC-
TITE®)
15. Use new one
1
2
3
4
5

TABLE OF CONTENTS
GENERAL INFORMATION 1
SPECIFICATIONS 2
REGULAR INSPECTION AND
ADJUSTMENTS 3
ENGINE 4
CHASSIS 5
ELECTRICAL 6
TUNING 7

CONTENTS
CHAPTER1
GENERAL
INFORMATION
DESCRIPTION................. 1-1
MACHINE
IDENTIFICATION.............1-2
INCLUDEDPARTS.......... 1-2
IMPORTANT
INFORMATION.................1-2
CHECKINGOF
CONNECTION..................1-3
SPECIALTOOLS............. 1-4
CONTROLFUNCTIONS.. 1-8
STARTINGAND
BREAK-IN........................ 1-8
TORQUE-CHECK
POINTS...........................1-11
CLEANINGAND
STORAGE......................1-1 2
CHAPTER2
SPECIFICATIONS
GENERAL
SPECIFICATIONS............2-1
MAINTENANCE
SPECIFICATIONS............2-3
TIGHTENING
TORQUES......................2-1 0
LUBRICATION
DIAGRAMS.................... 2-16
CABLEROUTING
DIAGRAM.......................2-18
CHAPTER3
REGULAR
INSPECTIONAND
ADJUSTMENTS
MAINTENANCE
INTERVALS......................3-1
PRE-OPERATION
INSPECTIONAND
MAINTENANCE................3-5
ENGINE............................3 -6
CHASSIS........................3-14
ELECTRICAL.................3-24
CHAPTER4
ENGINE
SEAT,FUEL TANK AND
SIDECOVERS.................. 4-1
EXHAUSTPIPE AND
SILENCER........................4-3
RADIATOR.......................4-5
CARBURETOR.................4-7
CAMSHAFTS..................4-14
CYLINDERHEAD...........4-19
VALVESAND
VALVESPRINGS...........4-22
CYLINDERAND
PISTON...........................4-26
CLUTCH.........................4- 29
OILFILTER ELEMENT
ANDWATER PUMP.......4-33
BALANCER....................4-37
OILPUMP....................... 4-39
KICKSHAFT AND
SHIFTSHAFT................. 4-42
CDIMAGNETO............... 4-47
ENGINEREMOVAL .......4-49
CRANKCASEAND
CRANKSHAFT...............4-53
TRANSMISSION,
SHIFTCAM AND
SHIFTFORK................... 4-59
CHAPTER5
CHASSIS
FRONTWHEEL AND
REARWHEEL ..................5-1
FRONTBRAKE AND
REARBRAKE ..................5-6
FRONTFORK................. 5-16
HANDLEBAR..................5-24
STEERING......................5-28
SWINGARM....................5-31
REARSHOCK
ABSORBER....................5-36
CHAPTER6
ELECTRICAL
ELECTRICAL
COMPONENTSAND
WIRINGDIAGRAM...........6-2
IGNITIONSYSTEM...........6-3
THROTTLEPOSITION
SENSORSYSTEM ...........6-6
CHAPTER7
TUNING
ENGINE.............................7-1
CHASSIS..........................7-6

1-1
DESCRIPTION
GENERALINFORMATION
DESCRIPTION
•The machine youhave purchased may differ slightly from those shown in the following.
•Designs and specificationsare subject to change without notice.
1. Clutchlever
2. Hotstarterlever
3. Frontbrakelever
4. Throttlegrip
5. Radiatorcap
6. Fueltankcap
7. Enginestopswitch
8. Kickstartercrank
9. Fueltank
10. Radiator
11. Coolant drain bolt
12. Rear brake pedal
13. Valve joint
14. Fuel cock
15. Cold starter knob
16. Drive chain
17. Air cleaner
18. Shift pedal
19. Oil dipstick
20. Front fork
1

1-2
MACHINEIDENTIFICATION
MACHINEIDENTIFICATION
Therearetwo significant reasons for
knowingtheserial number of your
machine:
1. When ordering parts, you can
givethenumber to your Yamaha
dealerforpositiveidentification of
themodelyou own.
2. If your machine isstolen, the au-
thoritieswillneed the number to
searchforand identify your ma-
chine.
VEHICLEIDENTIFICATION
NUMBER
Thevehicleidentification number "1"
isstampedonthe right of the steering
headpipe.
ENGINESERIALNUMBER
Theengineser ial number "1" is
stampedintothe e levated part of the
right-sideofthe engine.
MODELLABEL
Themodellabel "1" is affixed to the
frameunderthe rider's seat. This in-
formationwillbe needed to order
spareparts.
INCLUDEDPARTS
DETACHABLESIDESTAND
Thissidestand"1" is used to support
onlythemachine when standing or
transportingit.
•Never apply additionalforce to
thesidestand.
•Remove this sidestand before
startingout.
VALVEJOINT
Thisvalvejoint"1" prevents fuel from
flowingoutand is installedto the fuel
tankbreatherhose.
Inthisinstallation, make sure the
arrowfacesthe fuel tank and also
downward.
SPARKPLUGWRENCH
Thissparkplug wrench "1"is used to
removeandinst all the spark plug.
NIPPLEWRENCH
Thisnipplewrench "1" is used to
tightenthespoke.
JETNEEDLEPULL-UP TOOL
Thejetneedlepull-up tool "1" is used
topullthe jet needle out of the carbu-
retor.
HANDLEBARPROTECTOR
Installthehandlebar protector "1" so
thatthemark "a" face forward.
IMPORTANTINFORMATION
PREPARATIONFORREMOVAL
ANDDISASSEMBLY
1. Remove all dirt, mud, dust, and
foreignmaterialbefore removal
anddisassembly.
•When washing the machine with
highpressuredw ater, cover the
partsfollows.
Silencerexhaustport
Sidecoverair intake port
Waterpumphousing hole at the
bottom
Drainholeon the cylinder head
(rightside)
2. Use proper tools and cleaning
equipment.Referto "SPECIAL
TOOLS"section.
3. When disassembling thema-
chine,keepmatedparts together.
Theyincludegears, cylinders,
pistons,andother mated parts
thathavebeen "mated" through
normalwear.Mated parts must
bereusedas an asse mbly or re-
placed.

1-3
CHECKINGOF CONNECTION
4. During the machine disass embly,
cleanallparts and place them in
traysinthe order ofdisassembly.
Thiswillspeed up assem bly time
andhelpassure that all parts are
correctlyreinstalled.
5. Keep away from fire.
ALLREPLACEMENTPARTS
1. We recommend to use Yamaha
genuinepartsfor all replace-
ments.Useoil and/or grease rec-
ommendedbyYamaha for
assemblyandadjustment.
GASKETS,OILSEALS AND O-
RINGS
1. All gaskets, oil seals, and O-rings
shouldbere placed when an en-
gineisoverhauled. Allgasket sur-
faces,oilseal lips, and O-rings
mustbecleaned.
2. Properly oil all mating parts and
bearingsduringreassembly. Ap-
plygreaseto the oil seal lips.
LOCKWASHERS/PLATESAND
COTTERPINS
1. All lock washers/plates "1" and
cotterpinsmust be replaced
whentheyare removed. Lock
tab(s)shouldbe bent along the
boltornut flat(s) after the bolt or
nuthasbeen properly tightened.
BEARINGSANDOIL SEALS
1. Install the bearing(s)"1" and oil
seal(s)"2"with their manufactur-
er'smarksor numbers facing out-
ward.(Inother words, the
stampedlettersmust be on the
sideexposedto view.) When in-
stallingoilseal(s), apply a light
coatingoflightweightlithium base
greasetothe seal lip(s). Oil the
bearingsliberallywhen installing.
Donotuse compressed air to spin
thebearingsdry.This causes dam-
agetothe bearing surfaces.
CIRCLIPS
1. All circlips should be inspected
carefullybeforereassembly. Al-
waysreplacepistonpin clips after
oneuse.Replace distorted cir-
clips.Wheninstallinga circlip "1",
makesurethat the sharp-edged
corner"2"is posi tioned opposite
tothethrust "3" it receives. See
thesectionalv iew.
CHECKINGOF
CONNECTION
Dealingwithstains, rust, moisture,
etc.onthe connector.
1. Disconnect:
•Connector
2. Dry each terminal withan air
blower.
3. Connect and disconnect th e con-
nectortwoor th ree times.
4. Pull the lead to checkthat it will
notcomeoff.
5. If the terminal comes off, bend up
thepin"1" and reinsert the termi-
nalintothe connector.
6. Connect:
•Connector
Thetwoconnectors "click" together.
7. Check for continuity with a tester.
•If there in no continuity,clean the
terminals.
•Be sure to perform the steps1 to 7
listedabovewhen checking the
wireharness.
•For a field remedy, use a contac t re-
vitalizeravailableon the market.
•Use the tester onthe connector as
shown.

1-4
SPECIALTOOLS
SPECIALTOOLS
Toolname/Partnumber Howto use Illustration
Dialgaugeand stand
YU-3097,90890-01252
Stand
YU-1256
Thesetoolsare used to checkeach
partforrunout or bend.
Crankshaftinstallingtool
Crankshaftinstallingpot
YU-90050,90890-01274
Crankshaftinstallingbolt
YU-90050,90890-01275
Spacer(crankshaftinstaller)
YM-91044,90890-04081
Adapter(M12)
YU-90063,90890-01278
Thesetoolsare used to install the
crankshaft.
Pistonpinpuller set
YU-1304,90890-01304
Thistoolis used to remove the pis-
tonpin.
Radiatorcaptester
YU-24460-01,90890-01325
Radiatorcaptester adapter
YU-33984,90890-01352
Thesetoolsare used for checking
thecoolingsystem.
Rotorpuller
YM-04151,90890-04151
Thistoolis used to remove the fly-
wheelmagneto.
Steeringnutwrench
YU-33975,90890-01403
Thistoolis used when tighten the
steeringringnut to specification.

1-5
SPECIALTOOLS
Capboltwrench
YM-01500,90890-01500
Thistoolisused to loosen or tighten
thebasevalve.
Capboltring wrench
YM-01501,90890-01501
Thistoolisused to loosen or tighten
thedamperassembly.
Forksealdriver
YM-A0948,90890-01502
Thistoolisused when installthe fork
oilseal.
Spokenipplewrench
YM-01521,90890-01521
Thistoolis used to tighten the
spoke.
Pockettester
YU-3112-C,90890-03112
Usethistoolto inspect the coil resis-
tance,outputvoltage and amper-
age.
Timinglight
YM-33277-A,90890-03141
Thistoolis necessary for checking
ignitiontiming.
Valvespringcompressor
YM-4019,90890-04019
Thistoolis needed to remove and
installthevalve assemblies.
Toolname/Partnumber Howto use Illustration

1-6
SPECIALTOOLS
Clutchholdingtool
YM-91042,90890-04086
Thistoolis used to hold the clutch
whenremovingor installing the
clutchbosssecu ring nut.
Valveguideremover
Intake4.5mm (0.18 in)
Exhaust5.0mm (0.20 in)
YM-4116,90890-04116
YM-4097,90890-04097
Thistoolis needed to remove and
installthevalve guide.
Valveguideinstaller
Intake4.5mm (0.18 in)
Exhaust5.0mm (0.20 in)
YM-4117,90890-04117
YM-4098,90890-04098
Thistoolis needed to install the
valveguide.
Valveguidereamer
Intake4.5mm (0.18 in)
Exhaust5.0mm (0.20 in)
YM-4118,90890-04118
YM-4099,90890-04099
Thistoolis needed to rebore the
newvalveguide.
Crankcaseseparatingtool
YU-A9642
90890-04152
Thesetoolis used to remove the
crankshaftfromeither case.
Dynamicsparkteste r
YM-34487
Ignitionchecker
90890-06754
Thisinstrumentis necessary for
checkingtheignitionsystem compo-
nents.
Toolname/Partnumber Howto use Illustration

1-7
SPECIALTOOLS
Digitaltachometer
YU-39951-B,90890-06760
Thistoolis neededfor observing en-
ginerpm.
YAMAHABondNo. 1215 (ThreeB-
ond®No.1215)
90890-85505
Thissealant(Bond) is used for
crankcasematingsurface, etc.
Toolname/Partnumber Howto use Illustration

1-8
CONTROLFUNCTIONS
CONTROLFUNCTIONS
ENGINESTOPSWITCH
Theenginestop switc h "1" is located
ontheleft handlebar. Continue push-
ingtheengine stop switch till the en-
ginecomesto a stop.
CLUTCHLEVER
Theclutchlever "1"islocatedon the
lefthandlebar;it disengages or en-
gagestheclutch.Pull the clutch lever
tothehandlebar to disengage the
clutch,andrelease the lever to en-
gagetheclutch. The lever should be
pulledrapidlyandreleased slowly for
smoothstarts.
SHIFTPEDAL
Thegearratios of the constant-mesh
5speedtransmission are ideally
spaced.Thegears can be shifted by
usingtheshift pedal "1" on the left
sideofthe engine.
KICKSTARTERCRANK
Rotatethekickstarter crank "1" away
fromtheengine. Push the starter
downlightlywith your foot until the
gearsengage,then kick smoothly
andforcefullytostart the engine. This
modelhasaprimary kickstarter crank
sotheengine ca n be started in any
gearifthe clutch is disengaged. In
normalpractices,however, shift to
neutralbeforestarting.
THROTTLEGRIP
Thethrottlegrip "1" is located on the
righthandlebar;it accelerates or de-
celeratestheengine. For accelera-
tion,turnthe grip toward you; for
deceleration,turnit away from you.
FRONTBRAKELEVER
Thefrontbrakelever "1" is located on
therighthandlebar. Pull it toward the
handlebartoactivate the front brake.
REARBRAKEPEDAL
Therearbrakepedal "1" is located on
therightside of the machine. Press
downonthe brake pedal to activate
therearbrake.
FUELCOCK
Thefuelcock supplies fuel from the
tanktocarburetor and also filters the
fuel.Thefuel cock has the two posi-
tions:
OFF:
Withtheleverin this position, fuel will
notflow.Always return the lever to
thispositionwhen the engine is not
running.
ON:
Withthelever in this position, fuel
flowstothecarburetor. Normal riding
isdonewith the lever in this position.
COLDSTARTERKNOB
Whencold,the engine requires a
richerair-fuelmixture for starting. A
separatestartercircuit, which is con-
trolledbythe cold starter knob "1",
suppliesthismixture. Pull the cold
starterknoboutto open the circuit for
starting.Whenthe engine has
warmedup,push it in to cl ose the cir-
cuit.
HOTSTARTERLEVER
Thehotstarterlever "1" is used when
startingawarm engine. Use the hot
starterleverwhenstarting the engine
againimmediatelyafter it was
stopped(theengine is still warm).
Pullingthehot starter lever injects
secondaryairto thin the air-fuel mix-
turetemporarily,allowing the engine
tobestarted more easily.
STARTINGAND BREAK-IN
FUEL
Alwaysusetherecommended fuel as
statedbelow.Also, be sure to use
newgasolinethe day of a race.
Useonlyunleaded gasoline. The
useofleaded gasoline will cause
severedamageto the engine inter-
nalpartssuch as valves, piston
rings,andexhaust system, etc.
Recommendedfuel:
Premiumunleaded
gasolineonlywith a re-
searchoctanenumber
of95or higher.

1-9
STARTINGAND BREAK-IN
Ifknockingor pinging occurs, use a
differentbrandof gasoline or higher
octanegrade.
•For refueling,be sure to stop the
engineanduse enough care not
tospillany fuel. Also be sure to
avoidrefuelingclose to a fire.
•Refuel after the engine, exhaust
pipe,etc.have cooled off.
HANDLINGNOTE
Neverstartor run the engine in a
closedarea.The exhaust fumes
arepoisonous;they can cause
lossofconsciousness and death
inavery short time. Always oper-
atethemachinein a well-ventilated
area.
•The carburetor on this machine
hasabuilt-in accelerator pump.
Therefore,whenstarting the en-
gine,donot operate the throttle
orthespark plug will foul.
•Unlike a two-strokeengine, this
enginecannotbe kick started
whenthethrottle is open be-
causethekickstarter may kick
back.Also,if the throttle is open
theair/fuelmixture may be too
leanforthe engine to start.
•Before starting themachine, per-
formthechecksin the pre-opera-
tionchecklist.
AIRFILTERMAINTENANCE
Accordingto"CLEANING THE AIR
FILTERELEMENT"section in the
CHAPTER3,applythe foam-air-filter
oilorits equivalent to the element.
(Excessoilin the element may ad-
verselyaffectengine starting.)
STARTINGACOLD ENGINE
1. Inspect the coolant level.
2. Turn the fuel cock to "ON".
3. Shift the transmission into neutral.
4. Fully open the cold starterknob
"1".
5. Kick the kickstarter crank.
Donotopen the throttle while kick-
ingthekickstarter crank. Other-
wise,thekicks tarter crank may
kickback.
6. Return the cold starter knobto its
originalpositionand run the en-
gineat3,000–5,000 r/minfor 1 or
2minutes.
Sincethismode l is equipped with an
acceleratorpump,if the engine is
raced(thethrottle opened and
closed),theair/fuelmixture willbe too
richandthe engine may stall. Also
unlikeatwo-strokeengine,this model
canidle.
Donotwarm up the engine for ex-
tendedperiods of time.
STARTINGAWARM ENGINE
Donotoperate the cold starter knob
andthrottle.Pull the hot starter lever
"1"and start the engine by kicking
thekickstartercrank forcefully with a
firmstroke.As soon as the engine
starts,releasethe hot starter lever to
closetheair passage.
Restartinganengine after a fall
Pullthehot starter lever and startthe
engine.Assoonas the engine starts,
releasethehot starter lever to close
theairpassage.
Theenginefails to start
Pullthehot starter lever all the way
outandwhile ho lding the lever, kick
thekickstartercrank10 to 20 times to
cleartheengine.Then, restart the en-
gine.Referto "Restarting an engine
afterafall".
Observethefollowing break-in
proceduresduringinitialoperation
toensureoptimum performance
andavoidengine damage.
Thrott
le
grip
oper-
ation*
Cold
start-
er
knob
Hot
start-
erle-
ver
Star
ting
a
cold
en-
gine
Airtem-
perature=
lessthan
5°C(41
°F)
Open
3or4
times
ON OFF
Airtem-
perature=
morethan
5°C(41
°F)
None ON OFF
Airtem-
perature
(normal
tempera-
ture)=be-
tween5
°C(41°F)
and25°C
(77°F)
None ON/
OFF OFF
Airtem-
perature=
morethan
25°C(77
°F)
None OFF OFF
Startinganen-
gineaftera long
periodoftime
None ON OFF
Restartinga
warmengine None OFF ON
Restartingan
engineaftera
fall
None OFF ON
*Operatethe throttle grip before kic k
starting.

1-10
STARTINGAND BREAK-IN
BREAK-INPROCEDURES
1. Before starting the engine,fill the
fueltankwith the fuel.
2. Perform the pre-operation checks
onthemachine.
3. Start and warm up the engine.
Checktheidle speed, and check
theoperationof the controls and
theenginestop switch. Then, re-
starttheengine and check its op-
erationwithinno more than 5
minutesafterit is restarted.
4. Operate the machine in the lower
gearsatmoderate throttle open-
ingsforfive to eight minutes.
5. Check how the engine runs when
themachineis ridden with the
throttle1/4to1/2 open (low to me-
diumspeed)for about one hour.
6. Restart the engine and checkthe
operationofthemachine through-
outitsentire operating range. Re-
startthemachine and operate it
forabout10 to 15 more minutes.
Themachinewillnow be ready to
race.
•After the break-in or before each
race,youmust check the entire
machineforloose fittings and
fastenersasper "TORQUE-
CHECKPOINTS".Tighten all
suchfastenersas required.
•When any of the followingparts
havebeenreplaced, they must
bebrokenin.
CYLINDERANDCRANKSHAFT:
Aboutonehour of break-in oper-
ationisnecessary.
PISTON,RING,VALVES, CAM-
SHAFTSANDGEARS:
Thesepartsrequire about 30
minutesofbreak-in operation at
half-throttleor less. Observe the
conditionofthe engine carefully
duringoperation.