Yamaha YZ450FA 2011 Owner's Service Manual page 148

REMOVING THE CLUTCH BOSS
1. Remove:
• Nut "1"
• Conical washer "2"
• Clutch boss "3"
Use the clutch holding tool "4" to hold the clutch
boss.
Clutch holding tool:
YM-91042/90890-04086
A. For USA and CDN
B. Except for USA and CDN
CHECKING THE CLUTCH HOUSING AND
BOSS
1. Inspect:
• Clutch housing "1"
Cracks/wear/damage → Replace.
• Clutch boss "2"
Scoring/wear/damage → Replace.
CHECKING THE PRIMARY DRIVEN GEAR
1. Check:
• Circumferential play
Free play exists → Replace.
• Gear teeth "a"
Wear/damage → Replace.
CHECKING THE CLUTCH SPRINGS
1. Measure:
• Clutch spring free length "a"
Out of specification → Replace springs as a
set.
Clutch spring free length:
50.0 mm (1.97 in)
<Limit>: 49.0 mm (1.93 in)
CHECKING THE FRICTION PLATES
1. Measure:
• Friction plate thickness
Out of specification → Replace friction plate
as a set.
Measure at all four points.
Friction plate thickness:
2.92–3.08 mm (0.115–0.121 in)
<Limit>: 2.8 mm (0.110 in)
4-37
CLUTCH