Checking The Cylinder Head; Checking The Valve Spring; Checking The Valve - Yamaha F150A Service Manual

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.
1
Cylinder head warpage limit:
0.10 mm (0.0039 in)

Checking the valve spring

1. Measure the valve spring free length "a".
a
Valve spring free length "a":
48.08 mm (1.8929 in)
2. Measure the valve spring tilt "a". Replace
if above specification.
2
Valve spring tilt limit "a":

Checking the valve

1. Check the valve face. Replace if pitted or
worn.
2. Measure the valve margin thickness "a".
Valve margin thickness "a":
Intake:
Exhaust:
3. Measure the valve stem diameter "a".
7-41
a
1.7 mm (0.07 in)
0.40–0.80 mm (0.0157–0.0315 in)
0.80–1.20 mm (0.0315–0.0472 in)
a
Cylinder head
a
10
0
1
2
3
4
5
6
7
8
9
A