Yamaha TT-R90(R) Owner's Service Manual page 182

VALVES AND VALVE SPRINGS
Valve spring
1. Measure:
2. Measure:
Valve seat
1. Measure:
Measurement steps:
G
G
G
G
G
4 - 18
Valve spring free length a
G
Out of specification → Replace.
Free length (valve spring):
Intake:
28.32 mm (1.11 in)
<Limit>: 26.9 mm (1.06 in)
Exhaust:
28.32 mm (1.11 in)
<Limit>: 26.9 mm (1.06 in)
Spring tilt a
G
Out of specification → Replace.
Spring tilt limit:
Intake:
2.5˚/1.2 mm (0.05 in)
Exhaust:
2.5˚/1.2 mm (0.05 in)
Valve seat width a
G
Out of specification → Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
Apply Mechanic's blueing dye (Dykem) b
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. Where the
valve seat and valve face made contact,
blueing will have been removed.
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat
must be refaced.
ENG