Yamaha XC50V Service Manual page 172

VALVES AND VALVE SPRINGS
a. Apply a coarse lapping compound a to the
cC
a
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 be-
tween 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
b
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and
j. Measure the valve seat width c again. If
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valve face.
valve stem.
seat are evenly polished, then clean off all
of the lapping compound.
face and repeat the above steps.
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.
the valve seat width is out of specification,
reface and lap the valve seat.
ENG