Yamaha Raptor 90 YFM90RA 2011 Service Manual page 113

CAMSHAFT, ROCKER ARMS AND VALVES
2. Check:
• valve face
Pitting/wear → Grind the face.
• valve stem end
Mushroom shape or diameter larger than
the body of the stem → Replace.
3. Measure:
• margin thickness
Out of specification → Replace.
Margin thickness
Intake
0.5 ~ 0.9 mm
(0.0197 ~ 0.0354 in)
Exhaust
0.6 ~ 1.0 mm
(0.0236 ~ 0.0394 in)
4. Measure:
• runout (valve stem)
Out of specification → Replace.
Runout limit
0.02 mm (0.0008 in)
TIP
• When installing a new valve always replace
the guide.
• If the valve is removed or replaced always
replace the oil seal.
5. Eliminate:
• carbon deposits
(from the valve face and valve seat)
6. Check:
• valve seats
Pitting/wear → Reface the valve seat.
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