Yamaha YZ450FT Owner's Service Manual page 237

FRONT FORK
Base valve
1. Inspect:
• Base valve 1
Wear/damage → Replace.
Contamination → Clean.
• O-ring 2
Wear/damage → Replace.
• Bush 3
Wear/damage → Replace base valve.
• Spring 4
Damage/fatigue → Replace base valve.
• Air bleed screw 5
Wear/damage → Replace base valve.
EC554400
Fork spring
1. Measure:
• Fork spring free length a
Out of specification → Replace.
Fork spring free length:
Standard
465 mm (18.3 in)
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.
Inner tube bending limit:
0.2 mm (0.008 in)
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.
5 - 31
CHAS
<Limit>
460 mm (18.1 in)