Yamaha MX250 - Installing the Valves and Valve Springs

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ENGINE
VALVE
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.
INSTALLING THE VALVES AND VALVE SPRINGS
The following procedure applies to all of the valves, valve
springs and related components.
1.
Install:
• Valve stem seal (Intake side only)
•Valve “1”
• Valve spring “2”
• Valve spring retainer “3”
• Valve cotter “4”
Use the valve spring compressor “5” to install the
parts.
Do not let the lapping compound enter the gap
between the valve stem and the valve guide.
NOTICE
5
M
E
4
3
2
1
Valve spring compressor:
90890-01253
New
New
ab
• Do not compress the spring more than necessary.
• Surface “a” with the rounded edges of the valve cot-
ter must face downward (to the valve spring retainer
side) when installing it on top of the valve spring
retainer. If surface “b” of the opposite side is facing
downward when the valve cotter is installed, it could
result in the premature wear of the valve cotter.
NOTICE