Yamaha TT-R125EY, Service Manual

Page: 121 / 258

4-28
ENG
9. Lap:
• Valve face
• Valve seat
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and valve
face should be lapped.
Lapping steps:
• Apply a coarse lapping compound to the
valve face.
Do not let the compound enter the gap
between the valve stem and the valve
guide.
• Apply molybdenum disulfide oil to the valve
stem.
Measurement steps:
• Apply Mechanic’s blueing dye (Dykem)
b
to the valve face.
• Install the valve into the cylinder head.
• Press the valve through the valve guide and
onto the valve seat to make a clear pattern.
• Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
• If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
VALVES AND VALVE SPRINGS
8. Measure:
• Valve seat width a
Out of specification
→
Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
TIP
NOTICE