Yamaha WR450F, 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:
39.46 mm (1.55 in)
<Limit>: 38.46 mm (1.51 in)
Exhaust:
37.61 mm (1.48 in)
<Limit>: 36.61 mm (1.44 in)
Compressed spring force:
Intake:
130.2 ~ 149.8 N at 27.87 mm
(13.28 ~ 15.28 kg at 27.87 mm,
29.27 ~ 33.68 lb at 1.10 in)
Exhaust:
123.1 ~ 141.7 N at 28.38 mm
(12.55 ~ 14.45 kg at 28.38 mm,
27.67 ~ 31.85 lb at 1.12 in)
3. Measure:
• Spring tilt
a
Out of specification
→
Replace.
Spring tilt limit:
Intake:
2.5°/1.7 mm (0.067 in)
Exhaust:
2.5°/1.6 mm (0.063 in)
Valve lifter
1. Inspect:
• Valve lifter
Scratches/damage
→
Replace both lift-
ers and cylinder head.