Yamaha YFM7FGPW Service Manual page 188

VALVES AND VALVE SPRINGS
e. If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
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9. Lap:
• valve face
• valve seat
NOTE:
_
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
M MMM
a. Apply a coarse lapping compound to the
valve face.
CAUTION:
_
Do not let the compound enter the gap
between the valve stem and the valve
guide.
b. Apply molybdenum disulfide oil to the valve
stem.
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and valve
seat are evenly polished, then clean off all
of the compound.
NOTE:
_
For 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
face and repeat the above steps.
NOTE:
_
After every lapping operation be sure to clean
off all of the compound from the valve face and
valve seat.
f. Apply Mechanic's blueing dye (Dykem) to
the valve face.
g. Install the valve into the cylinder head.
4 - 30
ENG
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M MMM M M MMM M M MMM M M MMM
L L LLL L LLL
M M MMM M MMM