Yamaha XT660R Service Manual page 267

VALVES AND VALVE SPRINGS
4. Lap:
NOTE:
_
After replacing the cylinder head or replacing
the valve and valve guide, the valve seat and
valve face should be lapped.
M
a. Apply a coarse lapping compound a to the
_
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
b. Apply molybdenum disulfide oil onto the
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and valve
NOTE:
_
For the best lapping results, lightly tap the
valve seat while rotating the valve back and
forth between your hands.
e. Apply a fine lapping compound to the valve
f. After every lapping procedure, be sure to
g. Apply Mechanic's blueing dye (Dykem) b
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and
j. Measure the valve seat width again. If the
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5 - 28
• valve face
• valve seat
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valve face.
CAUTION:
valve stem.
seat are evenly polished, then clean off all
of the lapping compound.
face and repeat the steps above.
clean off all of the lapping compound from
the valve face and valve seat.
onto the valve face.
onto the valve seat to make a clear impres-
sion.
valve seat width is out of specification,
reface and lap the valve seat.
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ENG
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