Yamaha F150B, Service Manual

Page: 252 / 458

7-39
Power unit
POWR
Checking the valve spring
1. Measure the valve spring free length
a
.
Replace if out of specification.
2. Measure the valve spring tilt
b
. Replace
if above specification.
Checking the valve
1. Check the valve face. Replace if pitted or
worn.
2. Measure the valve margin thickness
a
.
3. Measure the valve stem diameter
b
.
Replace if out of specification.
4. Measure the valve stem runout. Replace
if above specification.
Cylinder head warpage limit:
0.1 mm (0.0039 in)
Valve spring free length
a
:
44.2 mm (1.74 in)
Valve spring tilt limit
b
: 1.2 mm (0.05 in)
a
b
a
Valve margin thickness
a
:
Intake:
0.70 mm (0.0276 in)
Exhaust:
1.00 mm (0.0394 in)
Valve stem diameter
b
:
Intake:
5.477–5.492 mm (0.2156–0.2162 in)
Exhaust:
5.464–5.479 mm (0.2151–0.2157 in)
Valve stem runout: 0.01 mm (0.0004 in)
b