Yamaha PZ50W Service Manual page 206

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 lapping compound.
NOTE:
For the best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
• Apply a fine lapping compound to the valve face
and repeat the above steps.
• After every lapping procedure, be sure to clean
off all of the lapping compound from the valve
face and valve seat.
• Apply Mechanic's blueing dye (Dykem) b onto
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 impression.
• Measure the valve seat width c again. If the
valve seat width is out of specification, reface
and lap the valve seat.
11. Measure:
• Valve spring free length a
Out of specification → Replace the valve
spring.
5-37
ENG
Valve spring free length:
Intake:
36.51 mm (1.44 in)
<Limit>: 34.68 mm (1.37 in)
Exhaust:
37.92 mm (1.49 in)
<Limit>: 36.02 mm (1.42 in)