lock YAMAHA YZ450F 2008 Owner's Manual

4-30
CLUTCH
14 Nut (clutch boss) 1 Refer to removal section.
15 Lock washer 1 Refer to removal section.
16 Clutch boss 1 Refer to removal section.
17 Thrust washer 1
18 Primary driven gear 1
19 Push lever shaft 1 Order Part name Q'ty Remarks

4-31
CLUTCH
REMOVING THE CLUTCH BOSS
1. Remove:
•Nut "1"
• Lock washer "2"
• Clutch boss "3"
Straighten the lock washer tab and
use the clutch holding tool "4" to hold
the clutch boss.
A. For USA and CDN
B. Except for USA and CDN
CHECKING THE CLUTCH
HOUSING AND BOSS
1. Inspect:
• Clutch housing "1"
Cracks/wear/damage
→Replace.
• Clutch boss "2"
Scoring/wear/damage
→Re-
place.
CHECKING THE PRIMARY DRIVEN
GEAR
1. Check:
• Circumferential play
Free play exists
→Replace.
• Gear teeth "a"
Wear/damage
→Replace.CHECKING THE CLUTCH
SPRINGS
1. Measure:
• Clutch spring free length "a"
Out of specification
→Replace
springs as a set.
CHECKING THE FRICTION
PLATES
1. Measure:
• Friction plate thickness
Out of specification
→Replace
friction plate as a set.
Measure at all four points.
CHECKING THE CLUTCH PLATES
1. Measure:
• Clutch plate warpage
Out of specification
→Replace
clutch plate as a set.
Use a surface plate "1" and thick-
ness gauge "2".
CHECKING THE PUSH LEVER
SHAFT
1. Inspect:
• Push lever shaft "1"Wear/damage
→Replace.
CHECKING THE PUSH ROD
1. Inspect:
• Push rod 1 "1"
• Bearing "2"
• Washer "3"
• Push rod 2 "4"
•Ball "5"
Wear/damage/bend
→Replace.
INSTALLING THE PUSH LEVER
SHAFT
1. Install:
• Push lever shaft "1"
• Apply the lithium soap base grease
on the oil seal lip.
• Apply the engine oil on the push le-
ver shaft.
INSTALLING THE CLUTCH
1. Install:
• Primary driven gear "1"
• Thrust washer "2"
• Clutch boss "3"
Apply the engine oil on the primary
driven gear inner circumference.
2. Install:
• Lock washer "1" Clutch holding tool:
YM-91042/90890-04086
Clutch spring free
length:
50.0 mm (1.97 in)
: 49.0 mm (1.93
in)
Friction plate thickness:
2.92–3.08 mm (0.115–
0.121 in)
: 2.8 mm (0.110
in)
Warp limit:
0.1 mm (0.004 in)

4-32
CLUTCH
• Nut (clutch boss) "2"
Make sure to tighten to specifica-
tion; otherwise, it may damage the
other part that is fastened togeth-
er.
• Install the lock washer with its con-
caves fitted over the convexes of
the clutch boss.
• Use the clutch holding tool "3" to
hold the clutch boss.
A. For USA and CDN
B. Except for USA and CDN
3. Bend the lock washer "1" tab.
4. Install:
• Friction plate "1"
• Clutch plate "2"
• Install the clutch plates and friction
plates alternately on the clutch
boss, starting with a friction plate
and ending with a friction plate.
• Apply the engine oil on the friction
plates and clutch plates.
5. Install:
•Bearing "1"
• Washer "2"
• Circlip "3"
To push rod 1 "4".
Apply the engine oil on the bearing
and washer.
6. Install:
• Push rod 2 "1"
• Ball "2"
• Push rod 1 "3"
Apply the engine oil on the push rod
1, 2 and ball.
7. Install:
• Pressure plate "1"
8. Install:
• Clutch spring
• Bolt (clutch spring)
Tighten the bolts in stage, using a
crisscross pattern.
9. Install:
• Gasket (clutch cover) "1"
• Dowel pin "2"
10. Install:
• Clutch cover "1"
• Bolt (clutch cover)
Tighten the bolts in stage, using a
crisscross pattern.
Nut (clutch boss):
75 Nm (7.5 m•kg, 54
ft•lb)
Clutch holding tool:
YM-91042/90890-04086
Bolt (clutch spring):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (clutch cover):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-37
BALANCER
BALANCER
REMOVING THE BALANCER
Order Part name Q'ty Remarks
Primary driven gear Refer to "CLUTCH" section.
Right crankcase cover Refer to "OIL FILTER ELEMENT AND WA-
TER PUMP" section.
Stator Refer to "CDI MAGNETO" section.
1 Nut (balancer) 1 Refer to removal section.
2 Nut (primary drive gear) 1 Refer to removal section.
3 Nut (balancer shaft driven gear) 1 Refer to removal section.
4 Lock washer 1
5 Balancer 1
6 Straight key 1
7 Conical washer 1
8 Primary drive gear 1
9 Balancer shaft drive gear 1
10 Lock washer 1
11 Balancer shaft driven gear 1

4-38
BALANCER
REMOVING THE BALANCER
1. Straighten the lock washer tab.
2. Loosen:
• Nut (balancer) "1"
• Nut (primary drive gear) "2"
• Nut (balancer shaft driven gear)
"3"
Place an aluminum plate "a" between
the teeth of the balancer shaft drive
gear "4" and driven gear "5".
CHECKING THE PRIMARY DRIVE
GEAR, BALANCER SHAFT DRIVE
GEAR AND BALANCER SHAFT
DRIVEN GEAR
1. Inspect:
• Primary drive gear "1"
• Balancer shaft drive gear "2"
• Balancer shaft driven gear "3"
Wear/damage
→Replace.
CHECKING THE BALANCER
1. Inspect:
• Balancer
Cracks/damage
→Replace.INSTALLING THE BALANCER
1. Install:
• Balancer shaft driven gear "1"
Install the balancer shaft driven gear
and balancer shaft with their lower
splines "a" aligning with each other.
2. Install:
• Balancer shaft driven gear "1"
• Align the punched mark "a" on the
balancer shaft drive gear with the
punched mark "b" on the balancer
shaft driven gear.
• Install the balancer shaft driven
gear and crankshaft with the lower
splines "c" aligning with each other.
3. Install:
• Lock washer "1"
• Nut (balancer shaft driven gear)
"2"
• Primary drive gear "3"
• Conical washer "4"
• Nut (primary drive gear) "5"
• Straight key "6"
• Balancer "7"
• Lock washer "8"• Nut (balancer) "9"
• Apply engine oil to the contact sur-
face and threaded portion of the nut
(primary drive gear).
• Place an aluminum plate "a" be-
tween the teeth of the balancer
shaft drive gear "10" and balancer
shaft driven gear "11".
• Install the conical washer with its
convex surface "b" outward.
4. Bend the lock washer tab.
Nut (balancer shaft driv-
en gear):
50 Nm (5.0 m•kg, 36
ft•lb)
Nut (primary drive gear):
110 Nm (11.0 m•kg, 80
ft•lb)
Nut (balancer):
45 Nm (4.5 m•kg, 33
ft•lb)

4-44
KICK SHAFT AND SHIFT SHAFT
REMOVING THE KICK SHAFT
ASSEMBLY
1. Remove:
• Kick shaft assembly "1"
Unhook the torsion spring "2" from
the hole "a" in the crankcase.
REMOVING THE SHIFT GUIDE
AND SHIFT LEVER ASSEMBLY
1. Remove:
• Bolt (shift guide)
• Shift guide "1"
• Shift lever assembly "2"
The shift lever assembly is disassem-
bled at the same time as the shift
guide.
REMOVING THE SEGMENT
1. Remove:
• Bolt (segment) "1"
• Segment "2"
Turn the segment counterclockwise
until it stops and loosen the bolt.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when removing the bolt.
CHECKING THE KICK SHAFT AND
RATCHET WHEEL
1. Check:
• Ratchet wheel "1" smooth move-
ment
Unsmooth movement
→Replace.• Kick shaft "2"
Wear/damage
→Replace.
• Spring "3"
Broken
→Replace.
CHECKING THE KICK GEAR, KICK
IDLE GEAR AND RATCHET
WHEEL
1. Inspect:
• Kick gear "1"
• Kick idle gear "2"
• Ratchet wheel "3"
• Gear teeth "a"
• Ratchet teeth "b"
Wear/damage
→Replace.
CHECKING THE SHIFT SHAFT
1. Inspect:
• Shift shaft "1"
Bend/damage
→Replace.
• Spring "2"
Broken
→Replace.
CHECKING THE SHIFT GUIDE AND
SHIFT LEVER ASSEMBLY
1. Inspect:
• Shift guide "1"
• Shift lever "2"
• Pawl "3"
• Pawl pin "4"
• Spring "5"
Wear/damage
→Replace.CHECKING THE STOPPER LEVER
1. Inspect:
• Stopper lever "1"
Wear/damage
→Replace.
• Torsion spring "2"
Broken
→Replace.
INSTALLING THE SEGMENT
1. Install:
• Segment "1"
• Bolt (segment)
Align the notch "a" on the segment
with the pin "b" on the shift cam.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when tightening the bolt.
INSTALLING THE STOPPER
LEVER
1. Install:
• Torsion spring "1"
• Washer "2"
• Stopper lever "3"
• Bolt (stopper lever) "4"
Align the stopper lever roller with the
slot on segment.
Bolt (segment):
30 Nm (3.0 m•kg, 22
ft•lb)
Bolt (stopper lever):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-46
KICK SHAFT AND SHIFT SHAFT
5. Hook:
• Torsion spring "1"
Turn the torsion spring clockwise and
hook into the proper hole "a" in the
crankcase.
INSTALLING THE KICK IDLE
GEAR
1. Install:
• Kick idle gear "1"
• Washer "2"
• Circlip "3"
• Apply the engine oil on the kick idle
gear inner circumference.
• Install the kick idle gear with its de-
pressed side "a" toward you.

4-50
ENGINE REMOVAL
Engine guard
1 Neutral switch 1
2 Drive chain sprocket cover 1
3 Nut (drive sprocket) 1 Refer to removal section.
4 Lock washer 1 Refer to removal section.
5 Drive sprocket 1 Refer to removal section.
6Clip 1
7 Bolt (brake pedal) 1
8 Brake pedal 1
9 Upper engine bracket 2
10 Lower engine bracket 2
11 Engine mounting bolt 3
12 Pivot shaft 1 Refer to removal section.
13 Engine 1 Refer to removal section. Order Part name Q'ty Remarks

4-51
ENGINE REMOVAL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE DRIVE
SPROCKET
1. Remove:
• Nut (drive sprocket) "1"
• Lock washer "2"
• Straighten the lock washer tab.
• Loosen the nut while applying the
rear brake.
2. Remove:
• Drive sprocket "1"
• Drive chain "2"
Remove the drive sprocket together
with the drive chain.
REMOVING THE ENGINE
1. Remove:
• Pivot shaft "1"
If the pivot shaft is pulled all the way
out, the swingarm will come loose. If
possible, insert a shaft of similar di-
ameter into the other side of the swin-
garm to support it.
2. Remove:
• Engine "1"
From right side.
Make sure that the couplers, hoses
and cables are disconnected.
INSTALLING THE ENGINE
1. Install:
• Engine "1"
Install the engine from right side.
• Pivot shaft "2"
• Engine mounting bolt (lower) "3"
• Lower engine bracket "4"
• Bolt (lower engine bracket) "5"
• Patch "6"
• Engine mounting bolt (front) "7"
• Upper engine bracket "8"
• Bolt (upper engine bracket) "9"
• Engine mounting bolt (upper) "10"
• Apply the molybdenum disulfide
grease on the pivot shaft.
• Install the patch with the claw "a"
facing outside the chassis.
INSTALLING THE BRAKE PEDAL
1. Install:
• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-rings and brake pedal
bracket.
INSTALLING THE DRIVE
SPROCKET
1. Install:
• Drive sprocket "1"
• Drive chain "2"
Install the drive sprocket together
with the drive chain.
Pivot shaft:
85 Nm (8.5 m•kg, 61
ft•lb)
Engine mounting bolt
(lower):
53Nm (5.3 m•kg, 38
ft•lb)
Bolt (lower engine brack-
et):
34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(front):
53 Nm (5.3 m•kg, 38
ft•lb)
Bolt (upper engine brack-
et):
55 Nm (5.5 m•kg, 40
ft•lb)
Engine mounting bolt
(upper):
55 Nm (5.5 m•kg, 40
ft•lb)
Bolt (brake pedal):
26 Nm (2.6 m•kg, 19
ft•lb)

4-52
ENGINE REMOVAL
2. Install:
• Lock washer "1"
• Nut (drive sprocket) "2"
Tighten the nut while applying the
rear brake.
Make sure to tighten to specifica-
tion; otherwise, it may damage the
other part that is fastened togeth-
er.
3. Bend the lock washer tab to lock
the nut.
4. Install:
• Drive chain sprocket guide
• Drive chain sprocket cover "1"
• Screw (drive chain sprocket cov-
er) "2"
INSTALLING THE NEUTRAL
SWITCH
1. Install:
• Spring "1"
•Pin "2"
• O-ring "3"
• Neutral switch "4"
• Screw (neutral switch) "5"
Apply the lithium soap base grease
on the O-ring.
Nut (drive sprocket):
75 Nm (7.5 m•kg, 54
ft•lb)
Screw (drive chain
sprocket cover):
8 Nm (0.8 m•kg, 5.8
ft•lb)
Screw (neutral switch):
4 Nm (0.4 m•kg, 2.9
ft•lb)