Yamaha YZ450F, Owner'S Service Manual

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ENG
VALVES AND VALVE SPRINGS
Valve spring
1. Measure:
• Valve spring free length
a
Out of specification
→
Replace.
2. Measure:
• Compressed spring force
a
Out of specification
→
Replace.
b
Installed length
Free length (valve spring):
Intake:
37.03 mm (1.46 in)
<Limit>: 36.03 mm (1.42 in)
Exhaust:
37.68 mm (1.48 in)
<Limit>: 36.68 mm (1.44 in)
Compressed spring force:
Intake:
111.3 ~ 127.9 N at 27.87 mm
(11.3 ~ 13.0 kg at 27.87 mm,
24.91 ~ 28.66 lb at 1.10 in)
Exhaust:
127.4 ~ 146.4 N at 27.38 mm
(13.0 ~ 14.9 kg at 27.38 mm,
28.66 ~ 32.85 lb at 1.08 in)
3. Measure:
• Spring tilt
a
Out of specification
→
Replace.
Spring tilt limit:
Intake:
2.5°/1.61 mm (0.063 in)
Exhaust:
2.5°/1.65 mm (0.065 in)
Valve lifter
1. Inspect:
• Valve lifter
Scratches/damage
→
Replace both lift-
ers and cylinder head.