Yamaha YZ450F(Y), Owner'S Manual

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5-19
FRONT FORK
CHECKING THE BASE VALVE 1. Inspect:
• Base valve "1"
Wear/damage → Replace. Contamination → Clean.
• O-ring "2"
Wear/damage → Replace. • Piston metal "3"
Wear/damage → Replace.
• Spring "4" Damage/fatigue → Replace base
valve.
• Air bleed screw "5" Wear/damage → Replace.
CHECKING THE COLLAR 1. Inspect:
• Piston metal "1"
Wear/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".
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 ADJUSTER 1. Inspect:
• Adjuster "1"
• O-ring "2"
Wear/damage → Replace.
ASSEMBLING THE FRONT FORK 1. Wash the all parts in a clean sol-
vent.
2. Stretch the damper assembly ful-
ly. 3. Fill:
• Front fork oil "1"
To damper assembly.
• 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.
4. After filling, pump the damper as- sembly "1" slowly up and down
(about 200 mm (7.9 in) stroke)
several times to bleed the damper
assembly of air.
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 2 to 4.
5. Measure:
• Oil level (left and right) "a" Out of specification → Adjust. Fork spring free length:
454 mm (17.9 in)
<Limit>: 449 mm (17.7
in)
Inner tube bending limit:
0.2 mm (0.008 in)
Recommended oil: Suspension oil "S1"
Oil capacity:
199 cm 3 (7.00 Imp oz, 6.73 US oz)
Standard oil level:
145-148 mm (5.71-5.83
in)
From top of fully
stretched damper as-
sembly.