2001 YAMAHA YZ426F oil

4 - 83
ENGCRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
11 Oil strainer 1
12 Oil delivery pipe 2 1
13 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
2

4 - 84
ENGCRANKCASE AND CRANKSHAFT
CRANKCASE BEARING
Extent of removal:1 Crankcase bearing removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE BEARING
REMOVAL
Preparation for removal Transmission
Shift cam and shift forkRefer to “TRANSMISSION, SHIFT
CAM AND SHIFT FORK” section.
1 Oil seal 3
2 Bearing 10 Refer to “REMOVAL POINTS”.
1

4 - 86
ENGCRANKCASE AND CRANKSHAFT
Crankshaft
1. Remove:
lCrankshaft 1
Use the crankcase separating tool 2.
CAUTION:
Do not use a hammer to drive out the
crankshaft.
Crankshaft bearing
1. Remove:
lBearing 1
NOTE:
lRemove the bearing from the crankcase by
pressing its inner race.
lDo not use the removed bearing.
Crankcase separating tool:
YU-1135-A/90890-01135
INSPECTION
Timing chain and timing chain guide
1. Inspect:
lTiming chain
Cracks/stiff ® Replace the timing chain
and camshaft sprocket as a set.
2. Inspect:
lTiming chain guide
Wear/damage ® Replace.
EC4N4101
Crankcase
1. Inspect:
lContacting surface a
Scratches ® Replace.
lEngine mounting boss b, crankcase
Cracks/damage ® Replace.
2. Inspect:
lBearing
Rotate inner race with a finger.
Rough spot/seizure ® Replace.
3. Inspect:
lOil seal
Wear/damage ® Replace.

4 - 87
ENGCRANKCASE AND CRANKSHAFT
EC4N4201
Crankshaft
1. Measure:
lRunout limit a
lSmall end free play limit b
lConnecting rod big end side clearance
c
lCrank width d
Out of specification ® Replace.
Use the dial gauge and a thickness
gauge.
Dial gauge and stand:
YU-3097/90890-01252
Standard
Runout
limit:0.03 mm
(0.0012 in)0.05 mm
(0.002 in)
Small end
free play:0.4 ~ 1.0 mm
(0.016 ~ 0.039 in)2.0 mm
(0.08 in)
Side
clearance:0.15 ~ 0.45 mm
(0.0059 ~ 0.0177 in)0.50 mm
(0.02 in)
Crack
width:61.95 ~ 62.00 mm
(2.439 ~ 2.441 in)—
Oil strainer
1. Inspect:
lOil strainer
Damage ® Replace.
Oil delivery pipe
1. Inspect:
lOil delivery pipe
Cracks/damage ® Replace.
lOil delivery pipe holes 1
Clogged ® Blow out with compressed
air.

4 - 89
ENGCRANKCASE AND CRANKSHAFT
2. Check:
lShifter operation
lTransmission operation
Unsmooth operation ® Repair.
3. Install:
lOil strainer 1
lBolt (oil strainer) 2
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
4. Apply:
lSealant
On the crankcase (right) 1.
NOTE:
Clean the contacting surface of crankcase (left
and right) before applying the sealant.
5. Install:
lDowel pin 1
lO-ring 2
lCrankcase (right)
To crankcase (left).
NOTE:
lFit the crankcase (right) onto the crankcase
(left). Tap lightly on the case with soft ham-
mer.
lWhen installing the crankcase, the connect-
ing rod should be positioned at TDC (top
dead center).
Quick gasket®:
ACC-QUICK-GS-KT
YAMAHA Bond No. 1215:
90890-85505
New

4 - 90
ENGCRANKCASE AND CRANKSHAFT
6. Tighten:
lHose guide 1
lClutch cable holder 2
lBolt (crankcase)
NOTE:
Tighten the crankcase tightening bolts in
stage, using a crisscross pattern.
T R..12 Nm (1.2 m · kg, 8.7 ft · lb)
7. Install:
lOil delivery pipe
lO-ring
lBolt (oil delivery pipe)
8. Install:
lTiming chain
lTiming chain guide (rear)
lBolt (timing chain guide)
9. Remove:
lSealant
Forced out on the cylinder mating sur-
face.
10. Apply:
lEngine oil
To the crank pin, bearing and oil deliv-
ery hole.
11. Check:
lCrankshaft and transmission operation.
Unsmooth operation ® Repair.
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4 - 93
ENG

TRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H4801
Shift fork, shift cam and segment
1. Inspect:
l
Shift fork
1

Wear/damage/scratches
®
Replace.
2. Inspect:
l
Shift cam
1

l
Segment
2

Bend/wear/damage
®
Replace.
3. Check:
lShift fork movement
Unsmooth operation ® Replace shift
fork.
NOTE:
For a malfunctioning shift fork, replace not only
the shift fork itself but the two gears each adja-
cent to the shift fork.
ASSEMBLY AND INSTALLATION
Transmission
1. Install:
l5th pinion gear (21T) 1
l3rd pinion gear (18T) 2
lCollar 3
l4th pinion gear (22T) 4
l2nd pinion gear (15T) 5
To main axle 6.
NOTE:
lApply the molybdenum disulfide oil on the
4th and 5th pinion gears inner circumference
and on the end surface.
lApply the molybdenum disulfide oil on the
2nd and 3rd pinion gears inner circumfer-
ence.

4 - 94
ENG

TRANSMISSION, SHIFT CAM AND SHIFT FORK
2. Install:
l
2nd wheel gear (23T)
1

l
4th wheel gear (24T)
2

l
3rd wheel gear (23T)
3

l
5th wheel gear (20T)
4

l
1st wheel gear (24T)
5

l
O-ring
6
To drive axle
7
.
NOTE:

l
Apply the molybdenum disulfide oil on the
1st, 2nd and 3rd wheel gears inner circum-
ference and on the end surface.
l
Apply the molybdenum disulfide oil on the
4th and 5th wheel gears inner circumfer-
ence.
l
Apply the lithium soap base grease on the O-
ring.
3. Install:
l
Plain washer
1

l
Circlip
2

NOTE:

l
Be sure the circlip sharp-edged corner
a
is
positioned opposite side to the plain washer
and gear
b
.
l
Be sure the circlip end
c
is positioned at
axle spline groove
d
.
New

4. Install:
l
Collar
1

NOTE:

l
Apply the lithium soap base grease on the oil
seal lip.
l
When installing the spacer into the crank-
case, pay careful attention to the crankcase
oil seal lip.