2001 YAMAHA WR 400F oil

4 - 45
ENGCYLINDER AND PISTON
3. Measure:
lRing end gap
Out of specification ® Replace.
NOTE:
You cannot measure the end gap on the
expander spacer of the oil control ring. If the oil
control ring rails show excessive gap, replace
all three rings.
End gap
Standard Limit
Top
ringWR426F:
0.20 ~ 0.30 mm
(0.008 ~ 0.012 in)
WR400F:
0.20 ~ 0.35 mm
(0.008 ~ 0.014 in)WR426F:
0.55 mm
(0.022 in)
WR400F:
0.60 mm
(0.024 in)
2nd
ringWR426F:
0.35 ~ 0.50 mm
(0.014 ~ 0.020 in)
WR400F:
0.40 ~ 0.55 mm
(0.016 ~ 0.022 in)WR426F:
0.85 mm
(0.033 in)
WR400F:
0.90 mm
(0.035 in)
Oil
ring0.20 ~ 0.50 mm
(0.01 ~ 0.02 in)—
Piston pin
1. Inspect:
lPiston pin
Blue discoloration/grooves ®
Replace, then inspect the lubrication
system.

4 - 46
ENGCYLINDER AND PISTON
2. Measure:
lPiston pin-to-piston clearance
ASSEMBLY AND INSTALLATION
Piston
1. Install:
lPiston rings
Onto the piston.
NOTE:
lBe sure to install the piston rings so that the
manufacturer’s marks or numbers are
located on the upper side of the rings.
lLubricate the piston and piston rings liberally
with engine oil. Measurement steps:
lMeasure the outside diameter (piston pin)
a.
If out of specification, replace the piston
pin
Outside diameter (piston pin):
WR426F: 18.991 ~ 19.000 mm
(0.7477 ~ 0.7480 in)
WR400F: 17.991 ~ 18.000 mm
(0.7083 ~ 0.7093 in)
lMeasure the inside diameter (piston) b.
Inside diameter (piston):
WR426F: 19.004 ~ 19.015 mm
(0.7482 ~ 0.7486 in)
WR400F: 18.004 ~ 18.015 mm
(0.7088 ~ 0.7093 in)
lCalculate the piston pin-to-piston clear-
ance with the following formula.
Piston pin-to-piston clearance =
Inside diameter (piston) b –
Outside diameter (piston pin) a
lIf out of specification, replace the piston.
Piston pin-to-piston clearance:
0.004 ~ 0.024 mm
(0.00016 ~ 0.00094 in)
: 0.07 mm (0.003 in)

4 - 47
ENG
2. Position:
lTop ring
l2nd ring
lOil ring
Offset the piston ring end gaps as
shown.
aTop ring end
b2nd ring end
cOil ring end (upper)
dOil ring
eOil ring end (lower)
45¡
135¡135¡
a
b ced
3. Install:
lPiston 1
lPiston pin 2
lPiston pin clips 3
NOTE:
lApply engine oil onto the piston pin and pis-
ton.
lBe sure that the arrow mark a on the piston
points to the exhaust side of the engine.
lBefore installing the piston pin clip, cover the
crankcase with a clean rag to prevent the
piston pin clip from falling into the crankcase.
lInstall the piston pin clips with their ends fac-
ing downward.
4. Lubricate:
lPiston
lPiston rings
lCylinder
NOTE:
Apply a liberal coating of engine oil.
Cylinder
1. Install:
lDowel pins
lO-ring
lGasket 1
lCylinder 2
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
lPass the timing chain 3 through the tim-
ing chain cavity.
lBe careful not to damage the timing chain
guide 4 during installation.
New
3New
New
CYLINDER AND PISTON

ENG
4 - 48
CLUTCH (WR426F)
CLUTCH (WR426F)
CLUTCH
Extent of removal:1 Push rod and push lever removal2 Push pod 1 disassembly
3 Friction plate and clutch plate removal4 Clutch housing removal
Extent of removal Order Part name Q’ty Remarks
CLUTCH REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Brake pedal Refer to “ENGINE REMOVAL” section.
Clutch cable Disconnect at engine side.
1 Clutch cover 1
2 Gasket 1
3 Dowel pin 2
4 Clutch spring 6
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8 Plain washer 1
9 Bearing 1
10 Ball 1
11Push rod 2
1
41
2
3
1

ENG
4 - 51
Reibscheiben
1. Messen:
lReibscheibenstärke
Unvorschriftsmäßig ® Die
Reibscheiben im Satz
erneuern.
Die Reibscheiben an vier
Stellen messen.
Kupplungsscheiben
1. Messen:
lVerzug der Kupplungsschei-
ben
Unvorschriftsmäßig ®
Kupplungsscheiben im Satz
erneuern.
Eine Richtplatte 1 und eine
Fühlerlehre 2 verwenden.
Reibscheibenstärke
2,9–3,1 mm
2,7 mm
Verzugsgrenze
0,1 mm
Druckhebel
1. Kontrollieren:
lDruckhebel 1
Verschleiß/Beschädigung ®
Erneuern.
Druckstangen
1. Kontrollieren:
lDruckstange 1 1
lLager 2
lBeilagscheibe 3
lDruckstange 2 4
lKugel 5
Verschleiß/Beschädigung/
Verbiegung ® Erneuern. Disque de friction
1. Mesurer:
lEpaisseur de disque de friction
Hors-spécification ® Changer
tous les disques de friction.
Mesurer chaque disque en qua-
tre endroits.
Disque d’embrayage
1. Mesurer:
lVoile de disque d’embrayage
Hors-spécification ® Changer
tous les disques d’embrayage.
Utiliser une plaque à surfacer
1 et une jauge d’épaisseur 2.
Epaisseur de disque de
friction:
2,9 à 3,1 mm
(0,114 à 0,122 in)
:
2,7 mm (0,106 in)
Limite de déformation:
0,1 mm (0,004 in)
Levier de poussée
1. Contrôler:
lLevier de poussée 1
Usure/endommagement ®
Changer.
Tige de poussée
1. Contrôler:
lTige de poussée 1 1
lRoulement 2
lRondelle ordinaire 3
lTige de poussée 2 4
lBille 5
Usure/endommagement/défor-
mation ® Changer.Disco de fricción
1. Medir:
lEspesor del disco de fricción
Fuera de especificaciones ®
Reemplazar el disco de fricción
como un juego.
Medir en los cuatro puntos.
Discos de embrague
1. Medir:
lAlabeo de los discos de embra-
gue
Fuera de especificaciones ®
Reemplazar los discos de
embrague como un juego.
Utilice un mármol de ajustador
1 y un juego de galgas 2.
Espesor del disco de fric-
ción:
2,9 ~ 3,1 mm
(0,114 ~ 0,122 in)
:
2,7 mm (0,106 in)
Límite de alabeo:
0,1 mm (0,004 in)
Palanca de empuje
1. Inspeccionar:
lPalanca de empuje 1
Desgaste/daños ® Reempla-
zar.
Varilla de empuje
1. Inspeccionar:
lVarilla de empuje 1 1
lCojinete 2
lArandela plana 3
lVarilla de empuje 2 4
lBola 5
Desgaste/daños/deformaciones
® Reemplazar.
KUPPLUNG (WR426F)
KUPPLUNG (WR426F)
EMBRAGUE (WR426F)

4 - 52
ENG

CLUTCH (WR426F)
EC4A5000
ASSEMBLY AND INSTALLATION
Push lever
1. Install:
l
Push lever
1

l
Bolt (push lever)
NOTE:

l
Apply the lithium soap base grease on the oil
seal lip.
l
Apply the engine oil on the push lever.
l
Fit the seat plate
2
in the groove
a
of the
push lever
1
and tighten the bolt (seat
plate).
2
1
a
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

Clutch
1. Install:
l
Seat plate
1

l
Clutch damper spring
2

l
Friction plate 1 [d = ø128 mm (5.04 in)]
3

l
Clutch plate
4

To clutch boss
5
.
NOTE:

Install the clutch damper spring with the “OUT
SIDE” mark
a
facing out.
4 3 2 1 5
a
3
5
1
24

2. Install:
l
Primary driven gear
1

l
Thrust washer
2

l
Clutch boss
3

NOTE:

Apply the engine oil on the primary driven gear
inner circumference.

4 - 53
ENG

CLUTCH (WR426F)
3. Install:
l
Lock washer
1

l
Nut (clutch boss)
2
NOTE:
Use the clutch holding tool 3 to hold the clutch
boss.
For USA and CDN
õExcept for USA and CDN
Clutch holding tool:
YM-91042/90890-04086
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)

õ
4. Bend the lock washer 1 tab.
5. Install:
lFriction plate 2 [d = ø119 mm (4.69 in)]
1
lClutch plate 2
NOTE:
lInstall the clutch plates and friction plates 2
alternately on the clutch boss, starting with a
friction plate and ending with a friction plate.
lApply the engine oil on the friction plates and
clutch plates.
6. Install:
lBearing 1
lPlain washer 2
lCirclip 3
To push rod 1 4.
NOTE:
Apply the engine oil on the bearing and plain
washer.
New

4 - 54
ENGCLUTCH (WR426F)
7. Install:
lPush rod 2 1
lBall 2
lPush rod 1 3
NOTE:
Apply the engine oil on the push rod 1, 2 and
ball.
8. Install:
lPressure plate 1
9. Install:
lClutch spring
lBolt (clutch spring)
NOTE:
Tighten the bolts in stage, using a crisscross
pattern.
T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
10. Install:
lGasket (clutch cover) 1
lDowel pin 2
New
11. Install:
lClutch cover 1
lBolt (clutch cover)
NOTE:
Tighten the bolts in stage, using a crisscross
pattern.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)