Yamaha XV19SX(C), Service Manual, Page: 293 / 494

VALVES AND VALVE SPRINGS
5-44
6. Measure:
• Valve stem runout
Out of specification
→
Replace the valve.
NOTE:
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always re-
place the valve stem seal.
EAS24300
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 width C “a”
Out of specification
→
Replace the cylinder
head.
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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 impres-
sion.
d. Measure the valve seat width.
NOTE:
Where the valve seat and valve face contacted
one another, the blueing will have been re-
moved.
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4. Lap:
• Valve face
• Valve seat
NOTE:
After replacing the cylinder head 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 “a” to the
valve face.
Valve stem runout
0.010 mm (0.0004 in)
Valve seat width C (intake)
1.10–1.30 mm (0.0433–0.0512 in)
Limit
2.0 mm (0.08 in)
Valve seat width C (exhaust)
1.10–1.30 mm (0.0433–0.0512 in)
Limit
2.0 mm (0.08 in)