engine YAMAHA WR 426F 2002 Owner's Manual

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
motorcycle 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

GEN
INFO
EINFAHRVORSCHRIFTEN
1. Vor dem Anlassen des Motors
volltanken.
2. Die “ROUTINEKONTROLLE
VOR FAHRTBEGINN” ausfüh-
ren.
3. Den Motor anlassen und
warmlaufen lassen. Dabei die
Leerlaufdrehzahl überwachen
und die Funktion der Bedie-
nungselemente sowie des Mo-
torstoppschalters “ENGINE
STOP” prüfen. Innerhalb der
nächsten fünf Minuten den
Motor wieder anlassen und die
folgenden Schritte ausführen.
4. Die Maschine fünf bis acht Mi-
nuten lang bei mäßiger Gas-
drehgrifföffnung in den unte-
ren Gängen fahren.
5. Den Motorbetrieb etwa eine
Stunde lang bei 1/4 bis 1/2 ge-
öffnetem Gasdrehgriff (niedri-
ge bis mittlere Geschwindig-
keit) überprüfen.
6. Den Motor erneut anlassen
und den Motorbetrieb im ge-
samten Betriebsbereich über-
prüfen. Den Motor abschalten
und noch einmal anlassen und
die Maschine 10 bis 15 Minu-
ten betreiben. Danach ist die
Maschine für Rennen einsatz-
bereit.
ACHTUNG:
Nach dem Einfahren und vor
jedem Rennen die Schraubver-
bindungen gemäß der Tabelle
“ANZUGSMOMENTE KONTROL-
LIEREN” auf festen Sitz prüfen
und vorschriftsmäßig anziehen.
Nach der Erneuerung eines der
folgenden Teile muß die
Maschine erneut eingefahren
werden.
- ZYLINDER UND KURBEL-
WELLE
Etwa eine Stunde Einfahrzeit
- KOLBEN, KOLBENRINGE, VEN-
TILE, NOKKENWELLEN UND -
RÄDER:
Etwa 30 Minuten Einfahrzeit bei
oder unter Halbgas (Sorgfältig
den Motorbetriebüberprüfen.)
MISE EN MARCHE ET RODAGE
ANLASSEN UND EINFAHREN
ARRANQUE Y RODAJE
PROCEDURE DE RODAGE
1. Avant de mettre le moteur en
marche, faire le plein d’essence.
2. Effectuer les contrôles avant utili-
sation de la machine.
3. Lancer le moteur et le laisser se
réchauffer. Vérifier le régime de
ralenti, le fonctionnement des
commandes et l’efficacité du bou-
ton d’arrêt du moteur “ENGINE
STOP”. Remettre ensuite le
moteur en marche et vérifier son
fonctionnement dans les 5 minutes
maximum.
4. Piloter la machine sur les rapports
inférieurs et à régime modéré
durant les cinq à huit premières
minutes. S’arrêter et vérifier l’état
de la bougie; elle devrait donner
des indices de richesse durant le
rodage.
5. Vérifier le fonctionnement du
moteur à une ouverture des gaz de
1/4 à 1/2 (petite à moyenne
vitesse) pendant environ 1 heure.
6. Remettre le moteur en marche et
vérifier son fonctionnement à
tous les régimes. Arrêter et véri-
fier la bougie. Relancer le moteur
et piloter la machine pendant 10 à
15 minutes supplémentaires. Elle
sera alors prête pour la course.
ATTENTION:
Après le rodage ou avant chaque
course, il faut vérifier toutes les fixa-
tions et serrages comme indiqué
dans “POINTS DE VERIFICA-
TION DE COUPLE DE SER-
RAGE”.
Serrer toutes ces fixations comme
requis.
Après avoir remplacé les pièces sui-
vantes, un nouveau rodage est
nécessaire.
CYLINDRE ET VILEBREQUIN:
Une heure environ de rodage est
nécessaire.
PISTONS, SEGMENTS, SOUPAPES,
ARBRES A CAMES
Ces pièces nécessitent un rodage de
30 minutes environ à une ouverture
des gaz de maximum 1/2. Surveiller
attentivement l’état du moteur pen-
dant la marche.PROCEDIMIENTOS DE RODAJE
1. Antes de arrancar el motor, llene
el depósito de combustible.
2. Realice las comprobaciones en el
vehículo previas a la conducción.
3. Arranque y deje que se caliente el
motor. Compruebe la velocidad
de ralentí, el funcionamiento de
los controles y el botón de parada
del motor “ENGINE STOP”. A
continuación, arranque nueva-
mente el motor y compruebe su
funcionamiento durante 5 minu-
tos como máximo después de
haberlo arrancado.
4. Maneje el vehículo en las mar-
chas inferiores y modere las aber-
turas del acelerador durante cinco
u ocho minutos.
5. Compruebe cómo funciona el
motor cuando maneje la motoci-
cleta con el acelerador 1/4 a 1/2
abierto (velocidad baja a mode-
rada) durante una hora aproxima-
damente.
6. Arranque el motor otra vez y
compruebe el funcionamiento del
vehículo en toda su gama de fun-
cionamiento. Arranque el motor y
maneje el vehículo durante otros
10 a 15 minutos. El vehículo ya
está preparado para la carrera.
PRECAUCION:
Después del rodaje o antes de cada
carrera, debe comprobar en todo el
vehículo la existencia de acopla-
mientos y remaches flojos así como
“TORSIONES-PUNTOS DE COM-
PROBACIÓN”.
En caso necesario, apriete todos los
remaches.
Cuando haya sustituido cualquiera
de las siguientes piezas, éstas deben
ser sometidas al rodaje.
CILINDRO Y CIGÜEÑAL:
Es necesario realizar aproximada-
mente una hora de conducción de
rodaje.
PISTÓN, ANILLO, VÁLVULAS,
ÁRBOLES DE LEVAS Y ENGRA-
NAJES:
Estas piezas requieren alrededor de
30 minutos de funcionamiento de
rodaje con el acelerador a la mitad o
inferior. Observe el estado del
motor cuidadosamente durante el
funcionamiento del mismo.
1 - 18

1 - 19
GEN
INFO
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
Frame construction
Combined seat and tank
Exhaust system
Engine mounting
Steering Steering shaft to
handlebar
Suspension Front Steering shaft to front
fork
Rear For link type
Rear Installation of shock
absorber
Rear Installation of swing-
arm
Wheel Installation of wheel Front
Rear
Brake Front
Rear
Fuel systemFrame to rear frame
Fuel tank to frame
Silencer to rear frame
Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering shaft to frame
Steering shaft to handle crown
Handle crown to handlebar
Front fork to handle crown
Front fork to under bracket
Assembly of links
Link to frame
Link to shock absorber
Link to swingarm
Shock absorber to frame
Tightening of pivot shaft
Tightening of front axle
Tightening of axle holder
Tightening of rear axle
Wheel to sprocket
Caliper to front fork
Brake disc to wheel
Tightening of union bolt
Master cylinder to handlebar
Tightening of air bleeder
Brake pedal to frame
Brake disc to wheel
Tightening of union bolt
Master cylinder to frame
Tightening of air bleeder
Fuel tank to fuel cock
NOTE:
Concerning the tightening torque, refer to
“MAINTENANCE SPECIFICATIONS” section
in the CHAPTER 2.

1 - 20
GEN
INFO
CLEANING AND STORAGE
FEC1B0000
CLEANING AND STORAGE
EC1B1000
CLEANING
Frequent cleaning of your machine will
enhance its appearance, maintain good overall
performance, and extend the life of many com-
ponents.
1. Before washing the machine, block off
the end of the exhaust pipe to prevent
water from entering. A plastic bag
secured with a rubber band may be used
for this purpose.
2. If the engine is excessively greasy, apply
some degreaser to it with a paint brush.
Do not apply degreaser to the chain,
sprockets, or wheel axles.
3. Rinse the dirt and degreaser off with a
garden hose; use only enough pressure
to do the job.
CAUTION:
Excessive hose pressure may cause water
seepage and contamination of wheel bear-
ings, front forks, brakes and transmission
seals. Many expensive repair bills have
resulted from improper high pressure
detergent applications such as those avail-
able in coin-operated car washers.
4. After the majority of the dirt has been
hosed off, wash all surfaces with warm
water and a mild detergent. Use an old
toothbrush to clean hard-to-reach places.
5. Rinse the machine off immediately with
clean water, and dry all surfaces with a
soft towel or cloth.
6. Immediately after washing, remove
excess water from the chain with a paper
towel and lubricate the chain to prevent
rust.
7. Clean the seat with a vinyl upholstery
cleaner to keep the cover pliable and
glossy.
8. Automotive wax may be applied to all
painted or chromed surfaces. Avoid com-
bination cleaner-waxes, as they may con-
tain abrasives.
9. After completing the above, start the
engine and allow it to idle for several min-
utes.

1 - 21
GEN
INFO
CLEANING AND STORAGE
EC1B2001
STORAGE
If your machine is to be stored for 60 days or
more, some preventive measures must be
taken to avoid deterioration. After cleaning the
machine thoroughly, prepare it for storage as
follows:
1. Drain the fuel tank, fuel lines, and the car-
buretor float bowl.
2. Remove the spark plug, pour a table-
spoon of SAE 10W-30 motor oil in the
spark plug hole, and reinstall the plug.
With the engine stop switch pushed in,
kick the engine over several times to coat
the cylinder walls with oil.
3. Remove the drive chain, clean it thor-
oughly with solvent, and lubricate it. Rein-
stall the chain or store it in a plastic bag
tied to the frame.
4. Lubricate all control cables.
5. Block the frame up to raise the wheels off
the ground.
6. Tie a plastic bag over the exhaust pipe
outlet to prevent moisture from entering.
7. If the machine is to be stored in a humid
or salt-air environment, coat all exposed
metal surfaces with a film of light oil. Do
not apply oil to rubber parts or the seat
cover.
NOTE:
Make any necessary repairs before the
machine is stored.

2 - 1
SPECGENERAL SPECIFICATIONS (WR426F)
EC200000
SPECIFICATIONS
EC211000
GENERAL SPECIFICATIONS (WR426F)
Model name: WR426FP (USA)
WR426F (EUROPE)
WR426F(P) (CDN, AUS, NZ, ZA)
Model code number: 5NG5 (USA)
5NG6 (EUROPE)
5NG8 (CDN, AUS, NZ, ZA)
Dimensions:
Overall length 2,171 mm (85.5 in)
Overall width 827 mm (32.6 in)
Overall height 1,303 mm (51.3 in)
Seat height 998 mm (39.3 in)
Wheelbase 1,490 mm (58.7 in)
Minimum ground clearance 373 mm (14.7 in)
Basic weight:
With oil and full fuel tank 121.5 kg (268 lb)
Engine:
Engine type Liquid cooled 4-stroke, DOHC
Cylinder arrangement Single cylinder, forward inclined
Displacement 426 cm
3 (15.0 Imp oz, 14.4 US oz)
Bore × stroke 95.0 × 60.1 mm (3.74 × 2.37 in)
Compression ratio 12.5 : 1
Starting system Kick starter
Lubrication system: Dry sump
Oil type or grade:
Engine oil
(For USA and CDN)
At 5 ˚C (40 ˚F) or higher Å
Yamalube 4 (20W-40) or SAE 20W-40 type SH
motor oil (Non-Friction modified)
At 15 ˚C (60 ˚F) or lower ı
Yamalube 4 (10W-30) or SAE 10W-30 type SH
motor oil (Non-Friction modified) and/or
Yamalube 4-R (15W-50) (Non-Friction modified)
(Except for USA and CDN)
API “SH” or higher grade
-20
-4-10
140
3010
5020
6830
8640 50
104
122°CTemp.
°F
10W-30
10W-40
20W-40
20W-50
15W-40

2 - 2
SPECGENERAL SPECIFICATIONS (WR426F)
Oil capacity:
Engine oil
Periodic oil change 1.3 L (1.14 Imp qt, 1.37 US qt)
With oil filter replacement 1.4 L (1.23 Imp qt, 1.48 US qt)
Total amount 1.5 L (1.32 Imp qt, 1.59 US qt)
Coolant capacity (including all routes): 1.2 L (1.06 Imp qt, 1.27 US qt)
Air filter: Wet type element
Fuel:
Type Premium unleaded gasoline only with a
research octane number of 95 or higher.
(Except for ZA)
Premium gasoline (For ZA)
Tank capacity 12 L (2.64 Imp gal, 3.17 US gal)
(For USA, CDN, AUS and NZ)
8.0 L (1.76 Imp gal, 2.11 US gal)
(For EUROPE and ZA)
Reserve 1.6 L (0.35 Imp gal, 0.42 US gal)
(For USA, CDN, AUS and NZ)
1.4 L (0.31 Imp gal, 0.37 US gal)
(For EUROPE and ZA)
Carburetor:
Type FCR-MX39
Manufacturer KEIHIN
Spark plug:
Type/manufacturer CR8E/NGK
U24ESR-N/DENSO
Gap 0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
Clutch type: Wet, multiple-disc
Transmission:
Primary reduction system Gear
Primary reduction ratio 62/21 (2.952)
Secondary reduction system Chain drive
Secondary reduction ratio 50/14 (3.571)
Transmission type Constant mesh, 5-speed
Operation Left foot operation
Gear ratio: 1st 29/12 (2.416)
2nd 26/15 (1.733)
3rd 21/16 (1.312)
4th 21/20 (1.050)
5th 21/25 (0.840)
Chassis:
Frame type Semi double cradle
Caster angle 27.8˚
Trail 123 mm (4.84 in)

2

2 - 4
SPECMAINTENANCE SPECIFICATIONS (WR426F)
MAINTENANCE SPECIFICATIONS (WR426F)
ENGINE
Item Standard Limit
Cylinder head:
Warp limit ---- 0.05 mm
(0.002 in)
Cylinder:
Bore size 95.00 ~ 95.01 mm
(3.7402 ~ 3.7406 in)----
Out of round limit ---- 0.05 mm
(0.002 in)
Camshaft:
Drive method Chain drive (left) ----
Camshaft cap inside diameter 22.000 ~ 22.021 mm
(0.8661 ~ 0.8670 in)----
Camshaft bearing diameter 21.967 ~ 21.980 mm
(0.8648 ~ 0.8654 in)----
Camshaft-to-cap clearance 0.020 ~ 0.054 mm
(0.0008 ~ 0.0021 in)0.08 mm
(0.003 in)
Cam dimensions
Intake“A”31.7 ~ 31.8 mm
(1.2480 ~ 1.2520 in)31.6 mm
(1.244 in)
“B”22.95 ~ 23.05 mm
(0.9035 ~ 0.9075 in)22.85 mm
(0.900 in)
Exhaust“A”31.2 ~ 31.3 mm
(1.2283 ~ 1.2323 in)31.1 mm
(1.224 in)
“B”22.95 ~ 23.05 mm
(0.9035 ~ 0.9075 in)22.85 mm
(0.900 in)
Camshaft runout limit ---- 0.03 mm
(0.0012 in)
A
B

2 - 7
SPECMAINTENANCE SPECIFICATIONS (WR426F)
Piston rings:
Top ring
Type Barrel ----
Dimensions (B × T) 1.2 × 3.5 mm (0.05 × 0.14 in) ----
End gap (installed) 0.20 ~ 0.30 mm
(0.008 ~ 0.012 in)0.55 mm
(0.022 in)
Side clearance (installed) 0.030 ~ 0.065 mm
(0.0012 ~ 0.0026 in)0.12 mm
(0.005 in)
2nd ring
Type Taper ----
Dimensions (B × T) 1.00 × 3.35 mm (0.04 × 0.13 in) ----
End gap (installed) 0.35 ~ 0.50 mm
(0.014 ~ 0.020 in)0.85 mm
(0.033 in)
Side clearance 0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)0.12 mm
(0.005 in)
Oil ring
Dimensions (B × T) 2.0 × 2.9 mm (0.08 × 0.11 in) ----
End gap (installed) 0.2 ~ 0.5 mm (0.01 ~ 0.02 in) ----
Crankshaft:
Crank width “A”61.95 ~ 62.00 mm
(2.439 ~ 2.441 in)----
Runout limit “C”0.03 mm (0.0012 in) 0.05 mm
(0.002 in)
Big end side clearance “D”0.15 ~ 0.45 mm
(0.0059 ~ 0.0177 in)0.50 mm
(0.02 in)
Small end free play “F”0.4 ~ 1.0 mm (0.02 ~ 0.04 in) 2.0 mm
(0.08 in)
Balancer:
Balancer drive method Gear ----
Decompression device:
Type Manual ----
Cable free play 5 ~ 9 mm (0.20 ~ 0.35 in)
Air filter oil grade: Engine oil ----Item Standard Limit
T
B
B
T
B
T

2 - 8
SPECMAINTENANCE SPECIFICATIONS (WR426F)
Clutch:
Friction plate thickness 2.9 ~ 3.1 mm (0.114 ~ 0.122 in) 2.7 mm
(0.106 in)
Quantity 9 ----
Clutch plate thickness 1.1 ~ 1.3 mm (0.043 ~ 0.051 in) ----
Quantity 8 ----
Warp limit ---- 0.1 mm
(0.004 in)
Clutch spring free length 48.4 mm (1.91 in) 47.4 mm
(1.87 in)
Quantity 6 ----
Clutch housing thrust clearance 0.10 ~ 0.35 mm
(0.0039 ~ 0.0138 in)----
Clutch housing radial clearance 0.010 ~ 0.044 mm
(0.0004 ~ 0.0017 in)----
Clutch release method Inner push, cam push ----
Shifter:
Shifter type Cam drum and guide bar ----
Guide bar bending limit ---- 0.05 mm
(0.002 in)
Kick starter:
Type Ratchet type ----
Carburetor:
USAEUROPE,
CDN, AUS, NZ,
ZA
I. D. mark 5NG5 50 5NG6 60 ----
Main jet (M.J) #165←----
Main air jet (M.A.J) #200←----
Jet needle-clip position (J.N) OBDRR-4 OBDQR-4 ----
Cutaway (C.A) 1.5←----
Pilot jet (P.J) #42←----
Pilot air jet (P.A.J) #75←----
Pilot outlet (P.O)ø0.9←----
Pilot screw (example) (P.S) 1-5/8 1-1/8 ----
Bypass (B.P)ø1.0←----
Valve seat size (V.S)ø3.8←----
Starter jet (G.S) #65←----
Float height (F.H) 8 mm (0.31 in)←----
Engine idle speed 1,700 ~
1,900 r/min←----
Intake vacuum 33.3 ~ 38.7 kPa
(250 ~ 290 mmHg,
9.84 ~ 11.42 inHg)←---- Item Standard Limit