Yamaha YP250R 2005, Service Manual

Page: 218 / 370

5 - 25
ENG
VALVES AND VALVE SPRINGS
b. Apply molybdenum disulfide oil to the valve
stem.
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and valve
seat are evenly polished, and 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 between 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
to
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 again. If the
valve seat width is out of specification,
reface and lap the valve seat.
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EAS00241
CHECKING THE VALVE SPRINGS
The following procedure applies to all of the
valve springs.
1. Measure:
• valve spring free length
a
Out of specification
→
Replace the valve
spring.
Valve spring free length
Intake and exhaust inner valve
spring
38.10 mm (1.50 in)
<Limit>: 36.10 mm (1.42 in)
Intake and exhaust outer valve
spring
36.93 mm (1.45 in)
<Limit>: 35.00 mm (1.38 in)