Checking The Valve Seats - Yamaha EH63 Service Manual

VALVES
1
2
3
4
5
6
7
8
9
10
5.
a

CHECKING THE VALVE SEATS

The following procedure applies to all of the valves and
valve seats.
1.
2.
a
3.
TIP
Do not rotate the valve while the valve face is contacting
the valve seat.
4.
a
Check:
• Valve spring contact surface "a"
More than 2/3 of the contact surface does not con-
tact  Replace.
Remove carbon deposits from the valve face and
valve seat.
Apply a small amount of coarse mechanic's blue lay-
out fluid to the valve face "a".
Insert the valve into the valve guide and use a valve
lapper to contact the valve face with the valve seat.
Measure:
• Valve face contact width "a"
Make sure that the contact width along the entire
valve face is within specifications.
Valve face contact width (Intake):
0.7–1.0 mm (0.0275–0.0393 in)
Valve face 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)
Out of specification/rough/eccentric
Replace.
3-38

wear