2008 YAMAHA WR 450F Owners Manual

6-16
FRONT FORK
FRONT FORK
REMOVING THE FRONT FORK
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
Front wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Front brake caliper Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Headlight
Handlebar Refer to "HANDLEBAR" section.
1 Protector 1
2 Pinch bolt (upper bracket) 2 Only loosening.
3 Cap bolt 1 Loosen when disassembling the front fork.
4 Pinch bolt (lower bracket) 2 Only loosening.
5 Front fork 1

6-17
FRONT FORK
DISASSEMBLING THE FRONT FORK
Order Part name Q'ty Remarks
1 Front fork cap bolt 1 Refer to removal section.
2 Fork spring 1 Drain the fork oil.
3 Dust seal 1 Refer to removal section.
4 Stopper ring 1 Refer to removal section.
5 Inner tube 1 Refer to removal section.
6 Outer tube 1
7 Piston metal 1
8 Slide metal 1
9 Oil seal washer 1
10 Oil seal 1
11 Spring guide 1
12 Base valve 1 Refer to removal section.
13 Damper rod 1 Refer to removal section.

6-18
FRONT FORK
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
The front fork requires careful atten-
tion. So it is recommended that the
front fork be maintained at the deal-
ers.
To prevent an accidental explosion
of air, the following instructions
should be observed:
• The front fork with a built-in pis-
ton rod has a very sophisticated
internal construction and is par-
ticularly sensitive to foreign ma-
terial. Use enough care not to
allow any foreign material to
come in when the oil is replaced
or when the front fork is disas-
sembled and reassembled.
• Before removing the cap bolts or
front forks, be sure to extract the
air from the air chamber com-
pletely.
REMOVING THE FRONT FORK
CAP BOLT
1. Remove:
• Front fork cap bolt "1"
From the outer tube.
Before removing the front fork from
the machine, loosen the front fork cap
bolt.
2. Remove:
• Front fork cap bolt "1"
Hold the locknut "2" and remove the
front fork cap bolt.
REMOVING THE INNER TUBE
1. Remove:
• Dust seal "1"
• Stopper ring "2"
Using slotted-head screwdriver.
Take care not to scratch the inner
tube.
2. Remove:
• Inner tube "1"
Oil seal removal steps:
a. Push in slowly "a" the inner tube
just before it bottoms out and then
pull it back quickly "b".
b. Repeat this step until the inner
tube can be pulled out from the
outer tube.
REMOVING THE DAMPER ROD
1. Remove:
• Base valve "1"
• Damper rod "2"
Use a damper rod holder "3" to lock
the damper rod.
CHECKING THE DAMPER ROD
1. Inspect:
• Damper rod "1"
Bend/damage→Replace damper
rod.
The front fork with a built-in piston
rod has a very sophisticated inter-
nal construction and is particularly
sensitive to foreign material.
Use enough care not to allow any
foreign material to come in when
the oil is replaced or when the
front fork is disassembled and re-
assembled.
CHECKING THE BASE VALVE
1. Inspect:
• Valve assembly "1"
Wear/damage →Replace.
• O-ring "2"
Damage→ Replace.
CHECKING THE FORK SPRING
1. Measure:
• Fork spring free length "a"
Out of specification→Replace.
CHECKING THE INNER TUBE
1. Inspect:
• Inner tube surface "a"
Score marks→Repair or replace.
Use #1,000 grit wet sandpaper.
Damaged oil lock piece→Re-
place.
• Inner tube bends
Out of specification→Replace.
Use the dial gauge "1".
Damper rod holder:
YM-01494/90890-01494
Fork spring free length:
460 mm (18.1 in)
: 455 mm (17.9
in)
Inner tube bending limit:
0.2 mm (0.008 in)

6-19
FRONT FORK
The bending value is shown by one
half of the dial gauge reading.
Do not attempt to straighten a bent
inner tube as this may dangerous-
ly weaken the tube.
CHECKING THE OUTER TUBE
1. Inspect:
• Outer tube "1"
Score marks/wear/damage→Re-
place.
CHECKING THE FRONT FORK
CAP BOLT
1. Inspect:
• Front fork cap bolt "1"
• O-ring "2"
• Air bleed screw "3"
Wear/damage→Replace.
ASSEMBLING THE FRONT FORK
1. Wash the all parts in a clean sol-
vent.
2. Install:
• Damper rod "1"
To inner tube "2".
To install the damper rod into the
inner tube, hold the inner tube
aslant. If the inner tube is held ver-
tically, the damper rod may fall into
it, damaging the valve inside.
3. Install:
• Copper washer "1"
• O-ring "2"
• Base valve "3"
To inner tube "4".
4. Tighten:
• Base valve "1"
• Use a damper rod holder "2" to lock
the damper rod "3".
• Apply the LOCTITE
® on the base
valve thread.
5. Install:
• Spring guide "1"
• Locknut "2"
To damper rod "3".
• Install the spring guide with its
smaller dia.end "a" facing down-
ward.
• With its thread "b" facing upward,
fully finger tighten the locknut onto
the damper rod.
6. Install:
• Dust seal "1"
• Stopper ring "2"
• Oil seal "3"
• Oil seal washer "4"
• Slide metal "5"
To inner tube "6".
• Apply the fork oil on the inner tube.
• When installing the oil seal, use vi-
nyl seat "a" with fork oil applied to
protect the oil seal lip.
• Install the oil seal with its manufac-
ture's marks or number facing the
axle holder side.
• Install the oil seal washer with its
projections "b" facing upward.
7. Install:
• Piston metal "1"
Install the piston metal onto the slot
on inner tube.
Base valve:
55 Nm (5.5 m•kg, 40
ft•lb)
Damper rod holder:
YM-01494/90890-01494

6-20
FRONT FORK
8. Install:
• Outer tube "1"
To inner tube "2".
9. Install:
• Slide metal "1"
• Oil seal washer "2"
To outer tube slot.
Press the slide metal into the outer
tube with fork seal driver "3".
10. Install:
• Oil seal "1"
Press the oil seal into the outer tube
with fork seal driver "2".
11. Install:
• Stopper ring "1"
Fit the stopper ring correctly in the
groove in the outer tube.
12. Install:
• Dust seal "1"
Apply the lithium soap base grease
on the inner tube.
13. Check:
• Inner tube smooth movement
Tightness/binding/rough spots →
Repeat the steps 2 to 12.
14. Compress the front fork fully.
15. Fill:
• Front fork oil
Until outer tube top surface with
recommended fork oil "1".
• Be sure to use recommended
fork oil. If other oils are used,
they may have an excessively ad-
verse effect on the front fork per-
formance.
• Never allow foreign materials to
enter the front fork.
16. After filling, pump the damper rod
"1" slowly up and down more than
10 times to distribute the fork oil.17. Fill:
• Front fork oil
Until outer tube top surface with
recom-mended fork oil once
more.
18. After filling, pump the outer tube
"1" slowly up and down (about
200 mm (7.9 in) stroke) to distrib-
ute the fork oil once more.
Be careful not to excessive full stroke.
A stroke of 200 mm (7.9 in) or more
will cause air to enter. In this case, re-
peat the steps 15 to 18.
19. Wait ten minutes until the air bub-
bles have been removed from the
front fork, and the oil has dis-
pense evenly in system before
setting recommended oil level.
Fill with the fork oil up to the top end
of the outer tube, or the fork oil will not
spread over to every part of the front
forks, thus making it impossible to ob-
tain the correct level.
Be sure to fill with the fork oil up to the
top of the outer tube and bleed the
front forks.
20. Measure:
• Oil level (left and right) "a"
Out of specification→Adjust. Fork seal driver:
YM-A0948/90890-01502
Fork seal driver:
YM-A0948/90890-01502
Recommended oil:
Suspension oil "S1"
Standard oil level:
132 mm (5.20 in)
*125 mm (4.92 in)
Extent of adjustment:
95–150 mm (3.74–5.91
in)
From top of outer tube
with inner tube and
damper rod "1" fully
compressed without
spring.
* For AUS, NZ, ZA and EUROPE

6-21
FRONT FORK
Be sure to install the spring guide "2"
when checking the oil level.
Never fail to make the oil level ad-
justment between the maximum
and minimum level and always ad-
just each front fork to the same
setting. Uneven adjustment can
cause poor handling and loss of
stability.
21. Measure:
• Distance "a"
Out of specification→Turn into
the locknut.
22. Loosen:
• Rebound damping adjuster "1"
• Loosen the rebound damping ad-
juster finger tight.
• Record the set position of the ad-
juster (the amount of turning out the
fully turned in posi-tion).
23. Install:
• Push rod "1"
• Fork spring "2"
• Install the fork spring with the
damper rod "3" pulled up.
• After installing the fork spring, hold
the damper rod end so that it will not
go down.
24. Install:
• Spring seat "1"
• Front fork cap bolt "2"
Fully finger tighten the front fork cap
bolt onto the damper rod.
25. Tighten:
• Front fork cap bolt (locknut) "1"
Hold the locknut "2" and tighten the
front fork cap bolt with specified
torque.
26. Install:
• Front fork cap bolt "1"
To outer tube.
Temporarily tighten the cap bolt.
27. Install:
• Protector guide "1"
Install the protector guide with its wid-
er side "a" facing downward.
INSTALLING THE FRONT FORK
1. Install:
• Front fork "1"
• Temporarily tighten the pinch bolts
(lower bracket).
• Do not tighten the pinch bolts (up-
per bracket) yet.
2. Tighten:
• Front fork cap bolt Distance "a":
18 mm (0.71 in) or more
Between damper rod
"1" top and locknut "2"
top.
Front fork cap bolt (lock-
nut):
29 Nm (2.9 m•kg, 21
ft•lb)
Front fork cap bolt:
30 Nm (3.0 m•kg, 22
ft•lb)

6-22
FRONT FORK
3. Adjust:
• Front fork top end "a"
4. Tighten:
• Pinch bolt (upper bracket) "1"
• Pinch bolt (lower bracket) "2"
Tighten the lower bracket to speci-
fied torque. If torqued too much, it
may cause the front fork to mal-
function.
5. Install:
• Speed sensor lead "1"
• Plate 1 "2"
• Bolt (plate 1) "3"
To right protector "4".
Install the speed sensor lead so that
its paint "a" directs as shown and
align the bottom "b" of the plate 1 with
the same paint.
6. Install:
• Speed sensor lead "1"
•Plate 2 "2"
• Screw (plate 2) "3"
To right protector "4".
Install the plate 2 in the direction as
shown.
7. Install:
• Protector "1"
• Bolt (protector) "2"
8. Adjust:
• Rebound damping force
Turn in the damping adjuster "1" fin-
ger-tight and then turn out to the orig-
inally set position.
Front fork top end (stan-
dard) "a":
Zero mm (Zero in)
Pinch bolt (upper brack-
et):
21 Nm (2.1 m•kg, 15
ft•lb)
Pinch bolt (lower brack-
et):
21 Nm (2.1 m•kg, 15
ft•lb)
Bolt (plate 1):
4 Nm (0.4 m•kg, 2.9 ft •
lb)
Screw (plate 2):
0.5 Nm (0.05 m•kg, 0.36
ft•lb)
Bolt (protector):
7 Nm (0.7 m•kg, 5.1
ft•lb)

6-23
HANDLEBAR
HANDLEBAR
REMOVING THE HANDLEBAR
Order Part name Q'ty Remarks
Headlight
1 Hot starter cable 1 Disconnect at the lever side.
2 Hot starter lever holder 1
3 Clutch cable 1 Disconnect at the lever side.
4 Clutch lever holder 1 Disconnect the clutch switch lead.
5 Engine stop switch 1 Disconnect the engine stop switch lead.
6 Brake master cylinder 1 Refer to removal section.
7 Start switch 1 Disconnect the start switch lead.
8 Throttle cable cap 1
9 Throttle cable #1 (pulled) 1 Disconnect at the throttle side.
10 Throttle cable #2 (pushed) 1 Disconnect at the throttle side.
11 Right grip 1 Refer to removal section.
12 Tube guide 1
13 Left grip 1 Refer to removal section.
14 Handlebar upper holder 2
15 Handlebar 1
16 Handlebar lower holder 2