Yamaha MX-800, Service Manual

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ENGINE
VALVES
6.
Measure:
• Valve spring tilt “a”
Out of specifications

Replace.
7.
Check:
• Valve spring contact surface “a”
More than 2/3 of the contact surface does not con-
tact

Replace.
CHECKING THE VALVE SEATS
The following procedure applies to all of the valves and
valve seats.
1.
Remove carbon deposits from the valve face and
valve seat.
2.
Apply a small amount of coarse mechanic’s blue lay-
out fluid to the valve face “a”.
3.
Insert the valve into the valve guide and use a valve
lapper to contact the valve face with the valve seat.
TIP
Do not rotate the valve while the valve face is contacting
the valve seat.
Installed compression spring force (Intake):
67.7 N (6.90 kgf, 15.2 lbf)
Installed compression spring force (Exhaust):
118.1 N (12.0 kgf, 26.5 lbf)
Installed length (Intake):
29.3 mm (1.1535 in)
Installed length (Exhaust):
29.0 mm (1.1417 in)
a
Tilt limit:
2.0 mm (0.0787 in)
a
a