Yamaha XC125 Service Manual page 52

I ENG INSPECTnON AND REPAIR
5. Repeat steps 2 and 3.
NOTE:
Be sure to clean off all compound from valve
face and valve seat after every lapping operation.
6. Inspect:
e Valve face
Not yet uniformly smooth -_ Repeat
procedure from step 1.
7. Apply:
e Mechanics bluing dye (Dykem)
(to valve face and seat)
8. Lap:
® Valve
9. Inspect:
® Valve face
Valve must make full seat contact indi-
cated by gray surface all around. The
_1 valve face where bluing was removed.
Faulty contact-_ Replace.
(See procedure below)
10. Clean:
® Intake/Exhaust port and valve assembly
(spray solvent with compre.ssed air)
NOTE:
After the lapping has been completed and the
valve assemblies have been reinstalled the valve
seal should be tested.
Pour solvent (_ into intake and exhaust ports,
There should be no leakage past the seat (_).
1 1. Check:
® Valve seal
Leakage past valve seat -_ Relap.
q
(See procedure below)
Relapping steps:
• Disassemble head parts.
o Repeat lapping steps using fine lapping
compound.
• Clean all parts thoroughly.
® Reassemble and check for leakage again
using solvent.
® Repeat steps as often as necessary to
achieve a satisfactory seal.
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