Yamaha TT-R125LW Owner's Service Manual page 238

VALVES AND VALVE SPRINGS
3. Inspect:
4. Measure:
5. Measure:
NOTE:
When installing a new valve always replace
the guide.
If the valve is removed or replaced always
replace the oil seal.
6. Eliminate:
7. Inspect:
4 - 27
Valve face
Pitting/wear → Grind the face.
Valve stem end
Mushroom shape or diameter larger
than the body of the stem → Replace.
Margin thickness a
Out of specification → Replace.
Margin thickness:
Intake:
0.4 ~ 0.8 mm
(0.0157 ~ 0.0315 in)
Exhaust:
0.8 ~ 1.2 mm
(0.0315 ~ 0.0472 in)
Runout (valve stem)
Out of specification → Replace.
Runout limit:
0.01 mm (0.0004 in)
Carbon deposits
(from the valve face and valve seat)
Valve seats
Pitting/wear → Reface the valve seat.
ENG