Yamaha YZFR6X(C) 2008 Service Manual page 231

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a. Apply Mechanic's blueing dye (Dykem) "b"
onto 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
impression.
d. Measure the valve seat width.
NOTE:
Where the valve seat and valve face contacted
one another, the blueing will have been
removed.
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4. Lap:
• Valve face
• Valve seat
EC2C01028
CAUTION:
This model uses titanium intake and
exhaust valves. Titanium valves that have
been used to lap the valve seats must not
be used. Always replace lapped valves with
new valves.
NOTE:
• When replacing the cylinder head, replace
the valves without lapping the valve seats
and valve faces.
• When replacing the valves or valve guides,
use new valves to lap the valve seats, and
then replace them with new valves.
VALVES AND VALVE SPRINGS
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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
seat are evenly polished, 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"
onto the valve face.
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