Checking The Valve Seats - Yamaha XSR 900 2022 Service Manual

5. Measure:
• Valve stem runout
Out of specification → Replace the valve.
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always re-
place the valve stem seal.
Valve stem runout
0.020 mm (0.0008 in)
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CHECKING THE VALVE SEATS

The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
• Carbon deposits
(from the valve face and valve seat)
2. Check:
• Valve seat
Pitting/wear → Replace the cylinder head.
3. Measure:
• Valve seat contact width "a"
Out of specification → Replace the cylinder
head.
Valve seat contact width limit (in-
take)
1.6 mm (0.06 in)
Valve seat contact width limit
(exhaust)
1.8 mm (0.07 in)
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VALVES AND VALVE SPRINGS
a. Apply blue layout fluid "b" onto the valve
face.
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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.
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.
a. Apply a coarse lapping compound "a" to the
valve face.
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NOTICE
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
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b. Apply molybdenum disulfide oil onto the
valve stem.
c. Install the valve into the cylinder head.
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