Yamaha F40B - Checking the Cylinder Head; Checking the Valve Spring; Checking the Valve

67C3K11 5-30
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Checking the cylinder head
1. Eliminate carbon deposits from the com-
bustion chambers and check the cylinder
head for damage or scratches.
2. Check the cylinder head warpage using a
straightedge 1 and thickness gauge 2
in the directions shown. Replace the cyl-
inder head assembly if above specifica-
tion.
Checking the valve spring
1. Measure the valve spring free length a.
Replace if below specification.
2. Measure the valve spring tilt b. Replace
if above specification.
Checking the valve
1. Check the valve face. Replace the valve
if pitted or worn.
2. Measure the valve margin thickness a.
Replace the valve if out of specification.
Cylinder head warpage limit:
0.10 mm (0.0039 in)
Valve spring free length a:
39.85 mm (1.5689 in)
S67C5073
2
1
S67C5074
S68V5775
a
Valve spring tilt limit b:
1.7 mm (0.067 in)
Valve margin thickness a:
Intake:
0.6–1.0 mm (0.024–0.039 in)
Exhaust:
0.7–1.1 mm (0.028–0.043 in)
Cylinder head