Yamaha Rhino 450 YXR45FAV Service Manual page 155

CAMSHAFT, ROCKER ARMS AND VALVES
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a. Apply Mechanic's blueing dye (Dykem) b to
the valve face.
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 pattern.
d. Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
e. If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
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9. Lap:
• valve face
• valve seat
NOTE:
After refacing the valve seat 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 to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
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, then clean off all
of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
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ENG
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