2003 YAMAHA YZ250LC oil

5-27
CHASFRONT FORK
Extent of removal Order Part name Q’ty Remarks
FRONT FORK DISASSEMBLY
1Cap bolt 1 Refer to “REMOVAL POINTS”.
2Fork spring 1 Drain the folk oil.
3Dust seal 1
4Stopper ring 1 Refer to “REMOVAL POINTS”.
5Inner tube 1
6Outer tube 1
7Piston metal 1
8Slide metal 1
9Plain washer 1
0Oil seal 1
qSpring guide 1
wBase valve 1 Use special tool.
eDamper rod 1 Refer to “REMOVAL POINTS”.
1
Extent of removal:1Oil seal removal2Damper rod removal
2






EC558000
FRONT FORK DISASSEMBLY
29 Nm (2.9 m•kg, 21 ft•lb)1 Nm (0.1 m•kg, 0.7 ft•lb)
30 Nm (3.0 m•kg, 22 ft•lb)
55 Nm (5.5 m•kg, 40 ft•lb)
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5-28
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.
cC
To prevent an accidental explosion of air,
the following instructions should be ob-
served:
9The 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 re-
placed or when the front fork is disassem-
bled and reassembled.
9Before removing the cap bolts or front
forks, be sure to extract the air from the air
chamber completely.
EC553000
REMOVAL POINTSEC553151
Cap bolt
1. Remove:
9Cap bolt 1
From the outer tube.
NOTE:
Before removing the front fork from the machine,
loosen the cap bolt.
2. Remove:
9Cap bolt 1
NOTE:
9While compressing the fork spring, set the thin
type spanners 2between the spacer 3and
spring guide 4.
9Hold the locknut 5and remove the cap bolt.
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5-29
CHASFRONT FORK
EC553201
Inner tube
1. Remove:
9Dust seal 1
9Stopper ring 2
Using slotted-head screwdriver.
cC
Take care not to scratch the inner tube.
2. Remove:
9Inner tube 1
EC553311
Damper rod
1. Remove:
9Base valve 1
9Damper rod 2
NOTE:
Use a damper rod holder 3to lock the
damper rod.
EC554000
INSPECTIONEC554100
Damper rod
1. Inspect:
9Damper rod 1
Bend/DamageReplace damper rod.
cC
The front fork with a built-in piston rod has
a very sophisticated internal construction
and is particularly sensitive to foreign ma-
terial.
Use enough care not to allow any foreign
material to come in when the oil is re-
placed or when the front fork is disassem-
bled and reassembled.
Oil seal removal steps:
9Push in slowly athe inner tube just be-
fore it bottoms out and then pull it back
quickly b.
9Repeat this step until the inner tube can
be pulled out from the outer tube.
Damper rod holder:
YM-1423/90890-01423
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5-30
CHASFRONT FORK
EC554200
Base valve
1. Inspect:
9Valve assembly 1
Wear/DamageReplace.
9O-ring 2
DamageReplace.
EC554400
Fork spring
1. Measure:
9Fork spring free length a
Out of specificationReplace.
EC554502
Inner tube
1. Inspect:
9Inner tube surface a
Score marksRepair or replace.
Use #1,000 grit wet sandpaper.
Damaged oil lock pieceReplace.
9Inner tube bends
Out of specificationReplace.
Use the dial gauge 1.
NOTE:
The bending value is shown by one half of the
dial gauge reading.
w
Do not attempt to straighten a bent inner
tube as this may dangerously weaken the
tube.
EC554600
Outer tube
1. Inspect:
9Outer tube 1
Score marks/Wear/DamageReplace.
Standard
460 mm 455 mm
(18.1 in) (17.9 in)Fork spring free length:
Inner tube bending limit:
0.2 mm (0.008 in)
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5-32
CHASFRONT FORK
5. Install:
9Spring guide 1
9Locknut 2
To damper rod 3.
NOTE:
9Install the spring guide with its cut afacing up-
ward.
9With its thread bfacing upward, fully finger
tighten the locknut onto the damper rod.
6. Install:
9Dust seal 1
9Stopper ring 2
9Oil seal 3
9Plain washer 4
9Slide metal 5
To inner tube 6.
NOTE:
9Apply the fork oil on the inner tube.
9When installing the oil seal, use vinyl seat a
with fork oil applied to protect the oil seal lip.
9Install the oil seal with its manufacture's marks
or number facing the axle holder side.
7. Install:
9Piston metal 1
NOTE:
Install the piston metal onto the slot on inner
tube.
8. Install:
9Outer tube 1
To inner tube 2.
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5-33
CHASFRONT FORK
9. Install:
9Slide metal 1
9Plain washer 2
To outer tube slot.
NOTE:
Press the slide metal into the outer tube with
fork seal driver 3.
10. Install:
9Oil seal 1
NOTE:
Press the oil seal into the outer tube with fork
seal driver 2.
11. Install:
9Stopper ring 1
NOTE:
Fit the stopper ring correctly in the groove in the
outer tube.
12. Install:
9Dust seal 1
NOTE:
Apply the lithium soap base grease on the inner
tube.
Fork seal driver:
YM-01442/90890-01442
Fork seal driver:
YM-01442/90890-01442
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5-34
CHASFRONT FORK
13. Check:
9Inner tube smooth movement
Tightness/Binding/Rough spots Repeat the
steps 2 to 12.
14. Compress the front fork fully.
15. Fill:
9Front fork oil
Until outer tube top surface with recom-
mended fork oil 1.
cC
9Be sure to use recommended fork oil. If
other oils are used, they may have an ex-
cessively adverse effect on the front fork
performance.
9Never allow foreign materials to enter the
front fork.
16. After filling, pump the damper rod 1slowly
up and down more than 10 times to distrib-
ute the fork oil.
17. Fill:
9Front fork oil
Until outer tube top surface with recom-
mended fork oil once more.
18. After filling, pump the outer tube 1slowly
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 en-
ter. In this case, repeat the steps 15 to 18.
Recommended oil:
Suspension oil “01”
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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:
9Oil level (left and right) a
Out of specification  Adjust.
NOTE:
Be sure to install the spring guide 2when
checking the oil level.
w
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:
135 mm (5.31 in)
Extent of adjustment:
80~150 mm (3.15~5.91 in)
From top of outer tube with
inner tube and damper rod
1 1
fully compressed without spring.
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