Yamaha XT660R S Service Manual page 266

VALVES AND VALVE SPRINGS
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2. Replace:
• valve guide
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
guide remover 1.
b. Install the new valve guide with the valve
guide installer 2 and valve guide remover
1.
c. After installing the valve guide, bore the
valve guide with the valve guide reamer 3
to obtain the proper valve-stem-to-valve-
guide clearance.
NOTE:
_
After replacing the valve guide, reface the
valve seat.
Valve guide remover (ø6)
90890-04064
Valve guide installer (ø6)
90890-04065
Valve guide reamer (ø6)
90890-04066
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3. Eliminate:
• carbon deposits
(from the valve face and valve seat)
4. Check:
• 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.
5. Measure:
• valve margin thickness a
Out of specification → Replace the valve.
Valve margin thickness
0.80 ~ 1.20 mm
(0.0315 ~ 0.0472 in)
ENG
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