Yamaha MX-800, Service Manual

Page: 71 / 188

3-31
1
2
3
4
5
6
7
8
9
10
ENGINE
VALVES
4.
Measure:
• Valve face contact width “a”
Make sure that the contact width along the entire
valve face is within specifications.
Out of specification/rough/eccentric wear

Replace.
5.
Measure:
• Valve seat contact width “a”
Make sure that the contact width along the entire
valve seat is within specifications.
Out of specification/rough/eccentric wear

Replace.
VALVE LAPPING
1.
Apply a coarse lapping compound evenly on the valve
face. Lap the valve by tapping and rotating the valve
lapper clockwise and counterclockwise.
2.
Clean off all of the lapping compound from the valve
face and valve seat. Apply fine lapping compound on
the valve face and lap the valve as described in step
1.
a
Valve face contact width (Intake):
0.9–1.1 mm (0.0354–0.0433 in)
Valve face contact width (Exhaust):
0.9–1.1 mm (0.0354–0.0433 in)
Limit (Intake):
1.6 mm (0.063 in)
Limit (Exhaust):
1.6 mm (0.063 in)
a
Valve seat contact width (Intake):
0.9–1.1 mm (0.0354–0.0433 in)
Valve seat contact width (Exhaust):
0.9–1.1 mm (0.0354–0.0433 in)
Limit (Intake):
1.6 mm (0.063 in)
Limit (Exhaust):
1.6 mm (0.063 in)