CHAPTER 4
ENGINE
SEAT, FUEL TANK
AND SIDE COVERS
..................................4-1
EXHAUST PIPE AND SILENCER
.............4-3
RADIATOR
................................................4-5
CARBURETOR
..........................................4-8
CAMSHAFTS
...........................................4-21
CYLINDER HEAD
....................................4-29
VALVES AND VALVE SPRINGS
............4-33
CYLINDER AND PISTON
........................4-42
CLUTCH
...................................................4-48
OIL FILTER, WATER PUMP
AND CRANKCASE COVER (RIGHT)
.....4-55
BALANCER
.............................................4-62
OIL PUMP
................................................4-65
KICK AXLE AND SHIFT SHAFT
.............4-69
AC MAGNETO
AND STARTER CLUTCH
........................4-76
ENGINE REMOVAL
.................................4-83
CRANKCASE AND CRANKSHAFT
........4-89
TRANSMISSION, SHIFT CAM
AND SHIFT FORK
...................................4-98
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL
.......5-1
FRONT BRAKE AND REAR BRAKE
.....5-11
FRONT FORK
..........................................5-27
HANDLEBAR
...........................................5-40
STEERING
...............................................5-46
SWINGARM
.............................................5-52
REAR SHOCK ABSORBER
....................5-60
GEN
INFO
1 - 1
DESCRIPTION
EC100000
GENERAL INFORMATION
EC110000
DESCRIPTION
1
Clutch lever
2
Hot starter lever
3
“ENGINE STOP” button
4
Trip meter
5
Main switch
6
Start switch
7
Front brake lever
8
Throttle grip
9
Radiator cap
0
Fuel tank cap
A
Taillight
B
Kickstarter
C
Fuel tank
D
Headlight
E
Radiator
F
Coolant drain bolt
G
Rear brake pedal
H
Valve joint
I
Fuel cock
J
Cold starter knob
K
Air cleaner
L
Drive chain
M
Shift pedal
N
Oil dipstick
O
Front fork
NOTE:
The machine you have purchased may differ
slightly from those shown in the following.
Designs and specifications are subject to
change without notice.
A
BCD
E
F G
1234
5
6
7
8
9 0
HI
J
K
L M
N O
GEN
INFO
1 - 8
SPECIAL TOOLS
YM-01442, 90890-01442 Fork seal driver
This tool is used when install the fork oil seal.YM-01442 90890-01442
YS-1880-A, 90890-01701 Sheave holder
This tool is used for when loosening or tightening the
flywheel magneto securing nut.YS-1880-A 90890-01701
YU-3112-C, 90890-03112 Yamaha pocket tester
Use this tool to inspect the coil resistance, output
voltage and amperage.YU-3112-C 90890-03112
YM-33277-A, 90890-03141 Timing light
This tool is necessary for checking ignition timing.YM-33277-A 90890-03141
YM-4019, 90890-04019 Valve spring compressor
This tool is needed to remove and install the valve
assemblies.YM-4019 90890-04019
YM-91042, 90890-04086 Clutch holding tool
This tool is used to hold the clutch when removing or
installing the clutch boss securing nut.YM-91042 90890-04086
YM-4116, 90890-04116
YM-4097, 90890-04097Valve guide remover
Intake 4.5 mm (0.18 in)
Exhaust 5.0 mm (0.20 in)
This tool is needed to remove and install the valve
guide.YM-4116
YM-409790890-04116
90890-04097
YM-4117, 90890-04117
YM-4098, 90890-04098Valve guide installer
Intake
Exhaust
This tool is needed to install the valve guide.YM-4117
YM-409890890-04117
90890-04098
YM-4118, 90890-04118
YM-4099, 90890-04099Valve guide reamer
Intake 4.5 mm (0.18 in)
Exhaust 5.0 mm (0.20 in)
This tool is needed to rebore the new valve guide.YM-4118
YM-4099 90890-04118
90890-04099
Part number Tool name/How to use Illustration
1 - 13
GEN
INFO
SIDESTAND
This sidestand 1 is used to support only the
machine when standing or transporting it.
WARNING
Never apply additional force to the side-
stand.
Hold up the sidestand before starting out.
1
EC15F000
VALVE JOINT
This valve joint 1 prevents fuel from flowing
out and is installed to the fuel tank breather
hose.
CAUTION:
In this installation, make sure the arrow
faces the fuel tank and also downward.
1
SPARK PLUG WRENCH
This spark plug wrench 1 is used to remove
and install the spark plug.
1
1
NIPPLE WRENCH
This nipple wrench 1 is used to tighten the
spoke.
CONTROL FUNCTIONS
1 - 14
GEN
INFO
FUEL
Always use the recommended fuel as stated
below. Also, be sure to use new gasoline the
day of a race.
CAUTION:
Use only unleaded gasoline. The use of
leaded gasoline will cause severe damage
to the engine internal parts such as valves,
piston rings, and exhaust system, etc.
NOTE:
If knocking or pinging occurs, use a different
brand of gasoline or higher octane grade.
WARNING
For refueling, be sure to stop the engine
and use enough care not to spill any fuel.
Also be sure to avoid refueling close to a
fire.
Refuel after the engine, exhaust pipe, etc.
have cooled off.
Recommended fuel:
Except for ZA:
Premium unleaded gasoline
only with a research octane
number of 95 or higher.
For ZA:
Premium gasoline
FUEL
GEN
INFO
KRAFTSTOFF
Ausschließlich den empfohlenen
Kraftstoff verwenden. Für Rennen fri-
schen Kraftstoff verwenden.
ACHTUNG:
Nur bleifreies Benzin verwenden.
Bei Verwendung von verbleitem
Benzin werden schwere Schäden
an internen Motorbauteilen wie
Ventilen, Kolbenringen, Auspuff-
systemen usw. verursacht.
HINWEIS:
Tritt bei hoher Last (Vollgas) Motor-
klingeln bzw. -klopfen auf, Marken-
kraftstoff eines renommierten Anbie-
ters oder Benzin mit höherer
Oktanzahl verwenden.
WARNUNG
Beim Tanken immer sicherstel-
len, daß der Motor gestoppt ist
und darauf achten, keinen Kraft-
stoff zu verschütten. Außerdem
niemals in der Nähe eines Feu-
ers Krafstoff einfüllen.
Erst Kraftstoff einfüllen, nach-
dem Auspuffrohr usw. abge-
kühlt sind.
Empfohlener Kraftstoff:
Nicht ZA:
Bleifreies Super-
benzin mit einer
Oktanzahl von
mind. 95
Nur ZA:
Superbenzin
ESSENCE
Toujours utiliser l’essence recommandée
décrite ci-dessous. D’autre part, s’assu-
rer d’utiliser de l’essence fraîche le jour
de la course.
ATTENTION:
Utiliser uniquement de l'essence sans
plomb. L'utilisation d'essence au
plomb entraînerait de graves domma-
ges aux parties internes du moteur
(valves, segments de piston, système
d'échappement, etc).
N.B.:
Si un cognement ou un cinglement sur-
vient, utiliser une marque d’essence dif-
férente ou une classe d’octane
supérieure.
AVERTISSEMENT
Avant de faire le plein, arrêter le
moteur. Faire attention de ne pas
répandre de carburant sur la
machine. Ne pas faire le plein près
d’une flamme.
Faire le plein après avoir laissé
refroidir le moteur, le tuyau
d’échappement, etc.
Essence préconisée:
Excepté pour ZA:
Essence super sans
plomb d’un indice
d’octane de recher-
che de 95 ou plus.
Pour ZA:
Essence super
COMBUSTIBLE
Utilice siempre el combustible recomen-
dado que se indica a continuación. Ade-
más, asegúrese de utilizar gasolina nueva
el día de la carrera.
ATENCION:
Utilice solamente gasolina sin plomo.
El uso de gasolina con plomo ocasio-
nará graves daños a las partes inter-
nas del motor como válvulas,
segmentos del pistón, y sistema de
escape, etc.
NOTA:
Si se produce un ruido de choque o un
zumbido, utilice una marca de gasolina
diferente o un grado de octano superior.
ADVERTENCIA
Cuando vaya a repostar, asegúrese
de parar el motor y de tener cuidado
suficiente para no derramar nada
de combustible. Además, asegúrese
de evitar repostar cerca de donde
haya fuego.
Reposte después de que el motor,
tubo de escape, etc., se hayan
enfriado.
Combustible recomen-
dado:
Excepto para ZA:
Solamente gasolina
súper sin plomo con
un número de octa-
nos de 95 o mayor.
Para ZA:
Gasolina súper
ESSENCE
KRAFTSTOFF
COMBUSTIBLE
1 - 14
1 - 18
GEN
INFO
BREAK-IN PROCEDURES
1. Before starting the engine, fill the fuel
tank with the fuel.
2. Perform the pre-operation checks on the
machine.
3. Start and warm up the engine. Check the
idle speed, and check the operation of
the controls and the “ENGINE STOP”
button. Then, restart the engine and
check its operation within no more than 5
minutes after it is restarted.
4. Operate the machine in the lower gears
at moderate throttle openings for five to
eight minutes.
5. Check how the engine runs when the
machine is ridden with the throttle 1/4 to
1/2 open (low to medium speed) for
about one hour.
6. Restart the engine and check the opera-
tion of the machine throughout its entire
operating range. Restart the machine
and operate it for about 10 to 15 more
minutes. The machine will now be ready
to race.
CAUTION:
After the break-in or before each race,
you must check the entire machine for
loose fittings and fasteners as per
“TORQUE-CHECK POINTS”.
Tighten all such fasteners as required.
When any of the following parts have
been replaced, they must be broken in.
CYLINDER AND CRANKSHAFT:
About one hour of break-in operation is
necessary.
PISTON, RING, VALVES, CAMSHAFTS
AND GEARS:
These parts require about 30 minutes of
break-in operation at half-throttle or less.
Observe the condition of the engine care-
fully during operation.
STARTING AND BREAK-IN
SPEC
2 - 5
MAINTENANCE SPECIFICATIONS
Cam chain:
Cam chain type/No. of links 98XRH2010-118M/118 ----
Cam chain adjustment method Automatic ----
Valve, valve seat, valve guide:
Valve clearance (cold) IN 0.10 ~ 0.15 mm
(0.0039 ~ 0.0059 in)----
EX 0.20 ~ 0.25 mm
(0.0079 ~ 0.0098 in)----
Valve dimensions:
“A” head diameter IN 26.9 ~ 27.1 mm
(1.0591 ~ 1.0669 in)----
EX 27.9 ~ 28.1 mm
(1.0984 ~ 1.1063 in)----
“B” face width IN 2.26 mm (0.089 in) ----
EX 2.26 mm (0.089 in) ----
“C” seat width IN 0.9 ~ 1.1 mm
(0.0354 ~ 0.0433 in)1.6 mm
(0.0630 in)
EX 0.9 ~ 1.1 mm
(0.0354 ~ 0.0433 in)1.6 mm
(0.0630 in)
“D” margin thickness IN 1 mm (0.0394 in) 0.85 mm
(0.033 in)
EX 1 mm (0.0394 in) 0.85 mm
(0.033 in)
Stem outside diameter IN 4.475 ~ 4.490 mm
(0.1762 ~ 0.1768 in)4.445 mm
(0.1750 in)
EX 4.965 ~ 4.980 mm
(0.1955 ~ 0.1961 in)4.935 mm
(0.1943 in)
Guide inside diameter IN 4.500 ~ 4.512 mm
(0.1772 ~ 0.1776 in)4.550 mm
(0.1791 in)
EX 5.000 ~ 5.012 mm
(0.1969 ~ 0.1973 in)5.050 mm
(0.1988 in)
Stem-to-guide clearance IN 0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)0.08 mm
(0.003 in)
EX 0.020 ~ 0.047 mm
(0.0008 ~ 0.0019 in)0.10 mm
(0.004 in)
Stem runout limit ---- 0.01 mm
(0.0004 in) Item Standard Limit
Head Diameter
B
Face WidthC
Seat Width
D
Margin ThicknessA