Yamaha F150A, Service Manual

Page: 266 / 493

7-41
Cylinder head
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Checking the cylinder head
1. Remove carbon deposits from the com-
bustion chambers, and then check the
cylinder head for damage and scratches.
2. Check the cylinder head warpage using a
straightedge “1” and a thickness gauge
“2” in 7 directions. Replace the cylinder
head if above specification.
Checking the valve spring
1. Measure the valve spring free length “a”.
2. Measure the valve spring tilt “a”. 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 “a”.
Cylinder head warpage limit:
0.10 mm (0.0039 in)
Valve spring free length “a”:
48.08 mm (1.8929 in)
2
1
a
Valve spring tilt limit “a”:
1.7 mm (0.07 in)
Valve margin thickness “a”:
Intake:
0.40–0.80 mm (0.0157–0.0315 in)
Exhaust:
0.80–1.20 mm (0.0315–0.0472 in)
a
a
a