2006 YAMAHA WR 450F fork oil

5 - 27
CHASFRONT FORK
EC558000
FRONT FORK DISASSEMBLY
Extent of removal:
1 Oil seal removal
2 Damper rod removal
Extent of removal Order Part name Q’ty Remarks
FRONT FORK DISASSEMBLY
1 Cap bolt 1 Refer to “REMOVAL POINTS”.
2 Fork spring 1 Drain the fork oil.
3 Dust seal 1
Refer to “REMOVAL POINTS”.
4 Stopper ring 1
5 Inner tube 1
6 Outer tube 1
7 Piston metal 1
8 Slide metal 1
9 Oil seal washer 1
0 Oil seal 1
A Spring guide 1
B Base valve 1 Use special tool.
C Damper rod 1 Refer to “REMOVAL POINTS”.
1
2

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CHASFRONT FORK
EC556000
HANDLING NOTE
NOTE:
The front fork requires careful attention. So it is
recommended that the front fork be maintained
at the dealers.
CAUTION:
To prevent an accidental explosion of air,
the following instructions should be
observed:
The front fork with a built-in piston rod
has a very sophisticated internal con-
struction 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 disas-
sembled and reassembled.
Before removing the cap bolts or front
forks, be sure to extract the air from the
air chamber completely.
EC553000
REMOVAL POINTS
EC553150
Cap bolt
1. Remove:
Cap bolt 1
From the outer tube.
NOTE:
Before removing the front fork from the
machine, loosen the cap bolt.
2. Remove:
Cap bolt 1
NOTE:
Hold the locknut 2 and remove the cap bolt.

5 - 29
CHAS
EC553201
Inner tube
1. Remove:
Dust seal 1
Stopper ring 2
Using slotted-head screwdriver.
CAUTION:
Take care not to scratch the inner tube.
2. Remove:
Inner tube 1
Oil seal removal steps:
Push in slowly a the inner tube just before
it bottoms out and then pull it back quickly
b.
Repeat this step until the inner tube can
be pulled out from the outer tube.
EC553311
Damper rod
1. Remove:
Base valve 1
Damper rod 2
NOTE:
Use a damper rod holder 3 to lock the damper
rod.
EC554000
INSPECTION
EC554100
Damper rod
1. Inspect:
Damper rod 1
Bend/damage → Replace damper rod.
CAUTION:
The front fork with a built-in piston rod has
a very sophisticated internal 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
reassembled.
Damper rod holder:
YM-01494/90890-01494
FRONT FORK

5 - 30
CHAS
EC554200
Base valve
1. Inspect:
Valve assembly 1
Wear/damage → Replace.
O-ring 2
Damage → Replace.
2
1
EC554400
Fork spring
1. Measure:
Fork spring free length a
Out of specification → Replace.
EC554502
Inner tube
1. Inspect:
Inner tube surface a
Score marks → Repair or replace.
Use #1,000 grit wet sandpaper.
Damaged oil lock piece → Replace.
Inner tube bends
Out of specification → Replace.
Use the dial gauge 1.
NOTE:
The bending value is shown by one half of the
dial gauge reading.
WARNING
Do not attempt to straighten a bent inner
tube as this may dangerously weaken the
tube.
EC554600
Outer tube
1. Inspect:
Outer tube 1
Score marks/wear/damage → Replace.
Fork spring free length:
Standard Limit
460 mm (18.1 in) 455 mm (17.9 in)
Inner tube bending limit:
0.2 mm (0.008 in)
FRONT FORK

5 - 32
CHASFRONT FORK
5. Install:
Spring guide 1
Locknut 2
To damper rod 3.
NOTE:
Install the spring guide with its smaller dia.
end a facing downward.
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.
NOTE:
Apply the fork oil on the inner tube.
When installing the oil seal, use vinyl seat a
with fork oil applied to protect the oil seal lip.
Install the oil seal with its manufacture’s
marks or number facing the axle holder side.
Install the oil seal washer with its projections
b facing upward.
New
New
7. Install:
Piston metal 1
NOTE:
Install the piston metal onto the slot on inner
tube.
New
8. Install:
Outer tube 1
To inner tube 2.

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CHASFRONT FORK
9. Install:
Slide metal 1
Oil seal washer 2
To outer tube slot.
NOTE:
Press the slide metal into the outer tube with
fork seal driver 3.
Fork seal driver:
YM-A0948/90890-01502
10. Install:
Oil seal 1
NOTE:
Press the oil seal into the outer tube with fork
seal driver 2.
Fork seal driver:
YM-A0948/90890-01502
11. Install:
Stopper ring 1
NOTE:
Fit the stopper ring correctly in the groove in
the outer tube.
12. Install:
Dust seal 1
NOTE:
Apply the lithium soap base grease on the
inner tube.

5 - 34
CHASFRONT FORK
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 recom-
mended fork oil 1.
CAUTION:
Be sure to use recommended fork oil. If
other oils are used, they may have an
excessively adverse effect on the front
fork performance.
Never allow foreign materials to enter the
front fork.
Recommended oil:
Suspension oil “S1”
16. After filling, pump the damper rod 1 slowly
up and down more than 10 times to distrib-
ute 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 distribute the fork oil once more.
NOTE:
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, repeat the steps 15 to 18.

5 - 35
CHASFRONT FORK
19. Wait ten minutes until the air bubbles have
been removed from the front fork, and the
oil has dispense evenly in system before
setting recommended oil level.
NOTE:
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 obtain 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.
* For EUROPE
** For AUS, NZ and ZA
NOTE:
Be sure to install the spring guide 2 when
checking the oil level.
WARNING
Never fail to make the oil level adjustment
between the maximum and minimum level
and always adjust each front fork to the
same setting. Uneven adjustment can
cause poor handling and loss of stability.
Standard oil level:
130 mm (5.12 in)
* 127 mm (5.00 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.