2000 YAMAHA YZ426F engine oil

4 - 39
ENGCYLINDER AND PISTON
Piston pin
1. Inspect:
lPiston pin
Blue discoloration/grooves ®
Replace, then inspect the lubrication
system.
2. Measure:
lPiston pin-to-piston clearance
Measurement steps:
lMeasure the outside diameter (piston pin)
a.
If out of specification, replace the piston
pin
Outside diameter (piston pin):
18.991 ~ 19.000 mm
(0.7477 ~ 0.7480 in)
lMeasure the inside diameter (piston) b.
Inside diameter (piston):
19.004 ~ 19.015 mm
(0.7482 ~ 0.7486 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:
0.009 ~ 0.025 mm
(0.00035 ~ 0.00098 in)
: 0.07 mm (0.003 in)
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.

4 - 40
ENGCYLINDER AND PISTON
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)
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.
4. Lubricate:
lPiston
lPiston rings
lCylinder
NOTE:
Apply a liberal coating of engine oil.
New
Cylinder
1. Install:
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
damper 4 during installation.
New

ENG

4 - 41
CLUTCH
CLUTCH
CLUTCH
Extent of removal:
1
Push rod and push lever removal
2
Push pod 1 disassembly
3
Friction plate and clutch plate removal
4
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 Push rod 2 1
4
1
1
2
3

4 - 44
ENG

CLUTCH
EC484500
Friction plate
1. Measure:
l
Friction plate thickness
Out of specification
®
Replace friction
plate as a set.
Measure at all four points.
EC484600
Clutch plate
1. Measure:
l
Clutch plate warpage
Out of specification
®
Replace clutch
plate as a set.
Use a surface plate
1
and thickness
gauge
2
.
Push lever
1. Inspect:
l
Push lever
1

Wear/damage
®
Replace.
Friction plate thickness:
2.9 ~ 3.1 mm
(0.114 ~ 0.122 in)
: 2.7 mm (0.106 in)
Warp limit:
0.1 mm (0.004 in)
EC484810
Push rod
1. Inspect:
l
Push rod 1
1

l
Bearing
2

l
Plain washer
3

l
Push rod 2
4

Wear/damage/bend
®
Replace.
EC495000
ASSEMBLY AND INSTALLATION
Push lever
1. Install:
l
Push lever
1

NOTE:

Apply the engine oil on the oil seal lip and push
lever.

4 - 45
ENG

CLUTCH
EC495221
Clutch
1. Install:
lLock washer 1
lNut (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
2. Bend the lock washer 1 tab.
3. Install:
lFriction plate 1
lClutch plate 2
NOTE:
lInstall the clutch plates and friction plates
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.
4. 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 - 46
ENGCLUTCH
5. Install:
lPush rod 2 1
lPush rod 1 2
NOTE:
Apply the engine oil on the push rod 1,2.
6. Install:
lPressure plate 1
7. 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)
8. Install:
lGasket (clutch cover) 1
lDowel pin 2
New
9. 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)

ENG
4 - 47
OIL FILTER, WATER PUMP AND CRANKCASE COVER
(RIGHT)
OIL FILTER, WATER PUMP AND CRANKCASE COVER (RIGHT)
OIL FILTER, WATER PUMP AND CRANKCASE COVER (RIGHT)
Extent of removal:1 Oil filter removal2 Water pump removal
3 Crankcase (right) removal
Extent of removal Order Part name Q’ty Remarks
OIL FILTER, WATER PUMP
AND CRANKCASE COVER
(RIGHT) REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Exhaust pipe Refer to “EXHAUST PIPE AND
SILENCER” section in the CHAPTER 3.
Brake pedal Refer to “ENGINE REMOVAL” section.
Clutch cover Refer to “CLUTCH” section.
1 Oil filter cover 1
Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
2 Oil filter 1
3 Coolant pipe 2 1
4 Water pump housing 1
5 Pin 2
6 Oil delivery pipe 1
1
23

4 - 51
ENG
OIL FILTER, WATER PUMP AND CRANKCASE COVER
(RIGHT)
EC4G5220
Impeller shaft
1. Install:
lImpeller shaft 1
lPlain washer 2
lImpeller shaft 3
NOTE:
lTake care so that the oil seal lip is not dam-
aged or the spring does not slip off its posi-
tion.
lWhen installing the impeller shaft, apply the
engine oil on the oil seal lip and impeller
shaft. And install the shaft while turning it.
lHold the impeller shaft on its width across
the flats a with spanners, etc. and remove
the impeller.
Crankcase cover (right)
1. Install:
lDowel pin 1
lO-ring 2
lCollar 3
lGasket 4 New
2. Install:
lCrankcase cover (right) 1
lBolt
NOTE:
lWhen installing the crankcase cover onto the
crankcase, be sure that the impeller shaft
end 2 aligns with the balancer end slot 3.
lTighten the bolts in stage, using a crisscross
pattern.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)