Yamaha RS90GTZ Service Manual page 262

VALVES AND VALVE SPRINGS
9. Measure:
• Valve seat width
Out of specification → Replace the cylinder
head.
Measurement steps:
• Apply Mechanic's blueing dye (Dykem)
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 impres-
sion.
• Measure the valve seat width.
TIP
Where the valve seat and valve face contacted
one another, the blueing will have been
removed.
5-37
ENG
Valve seat width:
Intake:
0.90 ~ 1.10 mm
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
Exhaust:
0.90 ~ 1.10 mm
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)