Yamaha BT1100 2002 Service Manual page 130

VALVE AND VALVE SPRINGS
4. Lap:
• valve face
• valve seat
NOTE:
After replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve
face should be lapped.
a. Apply a coarse lapping compound to the valve
face.
CAUTION:
Do not let the lapping compound enter the gap
between the valve stem and the valve guide.
b. Apply molybdenum disulfide oil onto 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 lapping compound.
NOTE:
For the best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hand.
e. Apply a fine lapping compound to the valve
face and repeat the above steps.
f. After every lapping procedure, be sure to
clean off all of the lapping compound from the
valve face and valve seat.
g. Apply Mechanic's blueing dye (Dykem) onto
the valve face.
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
j. Measure the valve seat width again. If the
valve seat width is out of specification, reface
and lap the valve seat.
4-25
ENG