Yamaha R1 Series 2015 Service Manual page 372

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 contact width.
TIP
Where the valve seat and valve face contacted
one another, the blue layout fluid will have been
removed.
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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.
ECA22580
NOTICE
This model uses titanium intake valves.
Titanium valves that have been used to lap
the valve seats must not be used. Always re-
place lapped valves with new valves.
TIP
• When replacing the intake valves, replace the
intake valves without lapping the valve seats
and valve faces.
• When replacing the cylinder head or intake
valve guides, use new valves to lap the valve
seats, and then replace them with new intake
valves.
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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.
VALVES AND VALVE SPRINGS
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.
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 blue layout fluid "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 contact width "c"
again. If the valve seat width is out of specifi-
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