Yamaha EH63 - Valve Lapping

VALVES
3-39
1
2
3
4
5
6
7
8
9
10
ENGINE
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 “1” 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.
3. Once the contacting surface of the valve face is pol-
ished and becomes shiny, apply mechanic’s blue lay-
out fluid to make sure that there are traces of even
contact in the center of the valve face.
TIP
After every lapping procedure, clean off the compound
from the valve face and valve seat.
a
Valve seat contact width (Intake):
0.7–1.0 mm (0.0275–0.0393 in)
Valve seat contact width (Exhaust):
0.7–1.0 mm (0.0275–0.0393 in)
Limit (Intake):
2.0 mm (0.0787 in)
Limit (Exhaust):
2.0 mm (0.0787 in)
1
Do not let the lapping compound enter the gap
between the valve stem and the valve guide.
NOTICE