2008 YAMAHA WR 450F engine

5-32
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→Replace.
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.
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)

5-33
CLUTCH
2. Install:
• Lock washer "1"
• 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 1 [t=2.0 mm (0.079
in)] "2"• Clutch plate 2 [t=1.6 mm (0.063
in)] "3"
• 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.
• Check the clutch plate for thickness
and install 4 thicker ones "a" on the
engine side and 3 thinner ones "b"
on the outside.
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)

5-34
OIL FILTER ELEMENT AND WATER PUMP
OIL FILTER ELEMENT AND WATER PUMP
REMOVING THE OIL FILTER ELEMENT AND WATER PUMP
Order Part name Q'ty Remarks
Right engine guard Refer to "ENGINE REMOVAL" section.
Drain the engine oil. Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
Drain the coolant. Refer to "CHANGING THE COOLANT" sec-
tion.
Exhaust pipe Refer to "EXHAUST PIPE AND SILENCER"
section.
Brake pedal Refer to "ENGINE REMOVAL" section.
Clutch cover Refer to "CLUTCH" section.
1 Oil filter element cover 1
2 Oil filter element 1
3 Coolant pipe 2 1
4 Water pump housing 1
5Pin 2
6 Oil tank breather hose 1
7 Kickstarter crank 1
8 Right crankcase cover 1
10 Nm (1.0 m kg, 7.2 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)
33 Nm (3.3 m kg, 24 ft lb)
14 Nm (1.4 m kg, 10 ft lb)
12 Nm (1.2 m kg, 8.7 ft lb)

5-36
OIL FILTER ELEMENT AND WATER PUMP
REMOVING THE IMPELLER
SHAFT
1. Remove:
• Impeller "1"
• Washer "2"
• Impeller shaft "3"
Hold the impeller shaft on its width
across the flats "a" with spanners,
etc. and remove the impeller.
REMOVING THE OIL SEAL
It is not necessary to disassemble the
water pump, unless there is an abnor-
mality such as excessive change in
coolant level, discoloration of coolant,
or milky transmission oil.
1. Remove:
• Bearing "1"
• Oil seal "2"
CHECKING THE IMPELLER SHAFT
1. Inspect:
• Impeller shaft "1"
Bend/wear/damage→Replace.
Fur deposits→Clean.CHECKING THE BEARING
1. Inspect:
•Bearing
Rotate inner race with a finger.
Rough spot/seizure→Replace.
CHECKING THE OIL SEAL
1. Inspect:
• Oil seal "1"
Wear/damage→Replace.
INSTALLING THE OIL SEAL
1. Install:
• Oil seal "1"
• Apply the lithium soap base grease
on the oil seal lip.
• Install the oil seal with its manufac-
ture's marks or numbers facing the
right crankcase cover "2".
2. Install:
•Bearing "1"
Install the bearing by pressing its out-
er race parallel.
INSTALLING THE IMPELLER
SHAFT
1. Install:
• Impeller shaft "1"
• Washer "2"
• Impeller "3"
• Take care so that the oil seal lip is
not damaged or the spring does not
slip off its position.
• When installing the impeller shaft,
apply the engine oil on the oil seal
lip, bearing and impeller shaft. And
install the shaft while turning it.
• Hold the impeller shaft on its width
across the flats "a" with spanners,
etc. and install the impeller.
INSTALLING THE RIGHT
CRANKCASE COVER
1. Install:
• Dowel pin "1"
• O-ring "2"
•Collar "3"
• Gasket "4"
Apply the lithium soap base grease
on the O-ring.
Impeller:
14 Nm (1.4 m•kg, 10
ft•lb)

5-37
OIL FILTER ELEMENT AND WATER PUMP
2. Install:
• Right crankcase cover "1"
•Bolt "2"
•Bolt
• Apply the engine oil on the impeller
shaft end.
• When installing the crankcase cov-
er onto the crankcase, be sure that
the impeller shaft end "2" aligns
with the balancer end slot "3".
• Tighten the bolts in stage, using a
crisscross pattern.
INSTALLING THE KICKSTARTER
CRANK
1. Install:
• Kickstarter crank "1"
• Washer
• Bolt (kickstarter crank)
Install so that there is a clearance "a"
of 8 mm (0.31 in) or more between
the kickstarter and frame and that the
kickstarter does not contact the
crankcase cover when it is pulled.
2. Install:
• Oil tank breather hose "1"
•Clamp "2"
INSTALLING THE WATER PUMP
HOUSING
1. Install:
• Dowel pin "1"
• O-ring "2"
Apply the lithium soap base grease
on the O-ring.
2. Install:
• Water pump housing "1"
• Bolt (water pump housing) "2"
• Washer "3"
• Coolant drain bolt "4"3. Install:
• O-ring "3"
• Coolant pipe "1"
• Bolt (coolant pipe) "2"
Apply the lithium soap base grease
on the O-ring.
INSTALLING THE OIL FILTER
ELEMENT
1. Install:
• Oil filter element "1"
• O-ring "2"
• Oil filter element cover "3"
• Bolt (oil filter element cover)
Apply the lithium soap base grease
on the O-ring.
Bolt:
12 Nm (1.2 m•kg, 8.7
ft•lb)
Bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (kickstarter crank):
33 Nm (3.3 m•kg, 24
ft•lb)Clamp:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (water pump hous-
ing):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Coolant drain bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (coolant pipe):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (oil filter element
cover):
10 Nm (1.0 m•kg, 7.2
ft•lb)

5-39
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)

5-42
OIL PUMP
CHECKING THE OIL PUMP
1. Inspect:
• Oil pump drive gear
• Oil pump drive shaft
• Rotor housing
• Oil pump cover
Cracks/wear/damage→Replace.
2. Measure:
• Tip clearance "a"
(between the inner rotor "1" and
outer rotor "2")
• Side clearance "b"
(between the outer rotor "2" and
rotor housing "3")
• Housing and rotor clearance "c"
(between the rotor housing "3"
and rotors "1" "2")
Out of specification→Replace the
oil pump assembly.
3. Check:
•Unsmooth→Repeat steps #1 and
#2 or replace the defective parts.INSTALLING THE OIL PUMP
1. Install:
• Oil pump drive shaft "1"
• Washer "2"
• Dowel pin "3"
• Inner rotor 1 "4"
• Apply the engine oil on the oil pump
drive shaft and inner rotor 1.
• Fit the dowel pin into the groove in
the inner rotor 1.
2. Install:
• Outer rotor 1 "1"
Apply the engine oil on the outer rotor
1.
3. Install:
• Oil pump cover "1"
• Screw (oil pump cover) "2"
• Dowel pin "3"
• Inner rotor 2 "4"
• Circlip "5"
• Apply the engine oil on the oil pump
drive shaft end and inner rotor 2.
• Fit the dowel pin into the groove in
the inner rotor 2.
4. Install:
• Outer rotor 2 "1"
• Dowel pin "2"
• Oil pump assembly "3"
• Bolt (oil pump assembly) "4"
Apply the engine oil on the outer rotor
2.
5. Install:
• Oil pump drive gear "1"
• Washer "2"
• Circlip"3"
Apply the engine oil on the oil pump
drive gear inner circumference.
Tip clearance "a":
0.12 mm or less (0.0047
in or less)
: 0.20 mm
(0.008 in)
Side clearance "b":
0.09–0.17 mm (0.0035–
0.0067 in)
: 0.24 mm
(0.009 in)
Housing and rotor clear-
ance "c":
0.03–0.10 mm (0.0012–
0.0039 in)
: 0.17 mm
(0.0067 in)
Screw (oil pump cover):
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (oil pump assem-
bly):
10 Nm (1.0 m•kg, 7.2
ft•lb)

5-46
KICK SHAFT AND SHIFT SHAFT
INSTALLING THE SHIFT GUIDE
AND SHIFT LEVER ASSEMBLY
1. Install:
• Spring "1"
• Pawl pin "2"
•Pawl "3"
To shift lever "4".
Apply the engine oil on the spring,
pawl pin and pawl.
2. Install:
• Shift lever assembly "1"
To shift guide "2".
3. Install:
• Shift lever assembly "1"
• Shift guide "2"
• The shift lever assembly is installed
at the same time as the shift guide.
• Apply the engine oil on the bolt
(segment) shaft.
4. Install:
• Bolt (shift guide) "1" INSTALLING THE SHIFT SHAFT
1. Install:
• Roller "1"
• Collar "2"
• Torsion spring "3"
• Washer "4"
• Shift shaft "5"
Apply the engine oil on the roller and
shift shaft.
2. Install:
• Shift pedal
Refer to "AC MAGNETO AND
STARTER CLUTCH" section.
INSTALLING THE KICK SHAFT
ASSEMBLY
1. Install:
• Kick gear "1"
• Washer "2"
• Circlip "3"
• Ratchet wheel "4"
• Spring "5"
• Washer "6"
• Circlip "7"
To kick shaft "8".
• Apply the molybdenum disulfide oil
on the inner circumferences of the
kick gear and ratchet wheel.
• Align the punch mark "a" on the
ratchet wheel with the punch mark
"b" on the kick shaft.
2. Install:
• Torsion spring "1"
To kick shaft "2".
Make sure the stopper "a" of the tor-
sion spring fits into the hole "b" on the
kick shaft.
3. Install:
• Spring guide "1"
Slide the spring guide into the kick
shaft, make sure the groove "a" in the
spring guide fits on the stopper of the
torsion spring.
4. Install:
• Kick shaft assembly "1"
• Washer "2"
• Apply the molybdenum disulfide
grease on the contacting surfaces
of the kick shaft stopper "a" and kick
shaft ratchet wheel guide "3".
• Apply the engine oil on the kick
shaft.
• Slide the kick shaft assembly into
the crankcase and make sure the
kick shaft stopper "a" fits into the
kick shaft ratchet wheel guide.
5. Hook:
• Torsion spring "1"
Turn the torsion spring clockwise and
hook into the proper hole "a" in the
crankcase.Bolt (shift guide):
10 Nm (1.0 m•kg, 7.2
ft•lb)