Yamaha 2004 YP400 Service Manual page 237

VALVES AND VALVE SPRINGS
2. Replace:
NOTE:
_
To ease valve guide removal and installation,
and to maintain the correct fit, heat the cylinder
head to 100 °C (212 °F) in an oven.
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a. Remove the valve guide with the valve
b. Install the new valve guide with the valve
c. After installing the valve guide, bore the
NOTE:
_
After replacing the valve guide, reface the
valve seat.
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3. Eliminate:
4. Check:
5. Measure:
5 - 24
• valve guide
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guide remover 1.
guide installer 2 and valve guide remover
1.
valve guide with the valve guide reamer 3
to obtain the proper valve-stem-to-valve-
guide clearance.
Valve guide remover (5 mm)
90890-04097, YM-04097
Valve guide installer (5 mm)
90890-04098, YM-04098
Valve guide reamer (5 mm)
90890-04099, YM-04099
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• carbon deposits
(from the valve face and valve seat)
• valve face
Pitting/wear → Grind the valve face.
• valve stem end
Mushroom shape or diameter larger than
the body of the valve stem → Replace the
valve.
• valve margin thickness a
Out of specification → Replace the valve.
Valve margin thickness
0.85 ~ 1.15 mm
(0.0394 ~ 0.0472 in)
ENG
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