Yamaha 2004 YXR660 Service Manual page 154

VALVES AND VALVE SPRINGS
3. Check:
• valve face
Pitting/wear → Grind the face.
• valve stem end
Mushroom shape or diameter larger than
the body of the stem → Replace.
4. Measure:
• margin thickness a
Out of specification → Replace.
5. Measure:
• valve stem runout
Out of specification → Replace.
NOTE:
• When installing a new valve always replace
the guide.
• If the valve is removed or replaced always
replace the oil seal.
6. Eliminate:
• carbon deposits
(from the valve face and valve seat)
7. Check:
• valve seats
Pitting/wear → Reface the valve seat.
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ENG
Margin thickness
Intake
0.85 ~ 1.15 mm
(0.0335 ~ 0.0453 in)
Exhaust
0.85 ~ 1.15 mm
(0.0335 ~ 0.0453 in)
Runout limit
0.01 mm (0.0004 in)