Yamaha F15MHX Manuel D'entretien page 242

POWR
CAMSHAFT AND VALVES
Valve lapping
NOTE:
After refacing the valve seat or replacing
the valve and valve guide, the valve seat
and valve face must be lapped.
Lapping steps:
8 Apply a coarse lapping compound to
the valve face.
cC
Make sure no compound enters the gap
between the valve stem and guide.
8 Apply molybdenum disulfide oil to
the valve stem.
8 Install the valve into the cylinder
head.
8 Turn the valve until the valve face
and valve seat are evenly polished,
then clean off all of the compound.
NOTE:
To obtain the best lapping results, light-
ly tap the valve seat while rotating the
valve back and forth between your
hands.
8 Apply fine lapping compound to
the valve face and repeat the above
steps.
NOTE:
Be sure to clean off all of the compound
on the valve face and valve seat after
every lapping operation.
8 Apply Mechanic's bluing dye to
the valve face.
8 Install the valve into the cylinder
head.
8 Press the valve through the valve
guide and onto the valve seat to mark
a clear pattern.
8 Measure the valve seat width again.
If the valve seat width is out of speci-
fication, reface and lap the valve seat.
5-30
E