Yamaha TT-R125 Manuel D'atelier Du Proprietaire page 316

VALVES AND VALVE SPRINGS
G
G
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
G
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
G
G
G
G
Valve spring
1. Measure:
4 - 29
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.
Valve spring free length a
G
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)
ENG