Checking The Valve Springs - Yamaha XT250X Service Manual

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.
NOTE:
Where the valve seat and valve face contacted
one another, the blueing will have been re-
moved.
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4. Lap:
Valve face
G
Valve seat
G
NOTE:
After replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve
face should be lapped.
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a. Apply a coarse lapping compound "a" to the
valve face.
ECA13790
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
VALVES AND VALVE SPRINGS
seat are evenly polished, then clean off all of
the lapping compound.
NOTE:
For the best lapping results, lightly tap the valve
seat while turning 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.
j. Measure the valve seat width "c" again. If the
valve seat width is out of specification, reface
and lap the valve seat.
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EAS24310

CHECKING THE VALVE SPRINGS

The following procedure applies to all of the
valve springs.
1. Measure:
Valve spring free length "a"
G
Out of specification → Replace the valve
spring.
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