Yamaha TTR125LM, Owner'S Service Manual

Page: 242 / 468

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ENG
VALVES AND VALVE SPRINGS
●
Install the valve into the cylinder head.
●
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
●
Apply a fine lapping compound to the
valve face and repeat the above steps.
●
Apply Mechanic’s blueing dye (Dykem) 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 again. If the
valve seat width is out of specification,
reface and re-lap the valve seat.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
Valve spring
1. Measure:
●
Valve spring free length
a
Out of specification
→
Replace.
Free length (valve spring):
Intake:
32.55 mm (1.28 in)
<Limit>: 31.2 mm (1.23 in)
Exhaust:
32.55 mm (1.28 in)
<Limit>: 31.2 mm (1.23 in)