Yamaha 2009 XP500Y TMAX Service Manual page 211

b. Install the valve into the cylinder head.
c. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
d. Measure the valve seat width.
TIP
Where the valve seat and valve face contacted
one another, the blueing will have been re-
moved.
L LLL L LLL L L LLL L L LLL L
4. Lap:
• Valve face
• Valve seat
TIP
After replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve
face should be lapped.
M MMM M MMM M M MMM M M MMM M
a. Apply a coarse lapping compound "a" to the
valve face.
ECA13790
NOTICE
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.
L LLL L L LLL L LLL
M MMM M M MMM M MMM
5-22
VALVES AND VALVE SPRINGS
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.
TIP
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
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) "b"
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.