Yamaha RX10H Service Manual page 184

VALVES AND VALVE SPRINGS
Lapping steps:
S Apply a coarse lapping compound a to the
valve face.
CAUTION:
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
S Apply molybdenum disulfide oil onto the valve
stem.
S Install the valve into the cylinder head.
S 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 be-
tween your hand.
S Apply a fine lapping compound to the valve
face and repeat the above steps.
S After every lapping procedure, be sure to
clean off all of the lapping compound from the
valve face and valve seat.
S Apply Mechanic's blueing dye (Dykem) onto
the valve face.
S Install the valve into the cylinder head.
S Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
S Measure the valve seat width a again. If the
valve seat width is out of specification, reface
and lap the valve seat.
11. Measure:
S Valve spring free length a
Out of specification ! Replace the valve
spring.
5-27
ENG
Free length (valve spring):
Intake
38.90 mm (1.53 in)
Exhaust
40.67 mm (1.60 in)