Yamaha TDM850 1996 Service Manual page 143

VALVE AND VALVE SPRING
Measurement steps:
S Apply the Mechanic's blueing dye (Dykem) b to
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 pattern.
S Measure the valve seat width. Where the valve
seat and valve face made contact, blueing will
have been removed.
S If the valve seat is too wide, too narrow, or the
seat is not centered, the valve seat must be re-
faced.
10. Lap:
S Valve face
S Valve seat
NOTE:
After refacing the valve seat or replacing the valve
and valve guide, the valve seat and valve face
should be lapped.
Lapping steps:
S Apply a coarse lapping compound a to the
valve face.
CAUTION:
Be sure no compound enters the gap between
the valve stem and guide.
S Apply molybdenum disulfide oil to 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 compound.
4-19
ENG