Checking The Piston Diameter; Checking The Cylinder Bore; Checking The Piston Ring; Checking The Piston Ring End Gap (Reference) - Yamaha F150B Service Manual

Checking the piston diameter

1. Measure the piston outside diameter at
the specified measuring point. Replace if
out of specification.
a
b
Piston diameter a:
93.921–93.941 mm (3.6977–3.6985 in)
Measuring point b:
14.0 mm (0.55 in) up from the bottom
of the piston skirt

Checking the cylinder bore

1. Measure the cylinder bore (D
measuring points a, b, and c, and in
direction d (D
, D
1 3
to the crankshaft, and direction e (D
D , D ), which is at a right angle to the
4 6
crankshaft.
a
b
D
2
c
D
4
D
6
a
20 mm (0.8 in)
b
60 mm (2.4 in)
c
100 mm (3.9 in)
Cylinder bore (D –D ):
1 6
94.000–94.017 mm (3.7008–3.7014 in)

Checking the piston ring

1. Check the piston ring dimensions B and
T. Replace the piston ring set if out of
specification.
–D ) at
1 6
, D ), which is parallel
5
,
2
D
1
d
D e
3
D
5
a
B
T
c
T
Piston ring dimensions:
Top ring a:
B:1.17–1.19 mm (0.0461–0.0469 in)
T:2.80–3.00 mm (0.1102–0.1181 in)
Second ring b:
B:1.17–1.19 mm (0.0461–0.0469 in)
T:3.70–3.90 mm (0.1457–0.1535 in)
Oil ring c:
B:2.40–2.47 mm (0.0945–0.0972 in)
T:2.30–2.70 mm (0.0906–0.1063 in)
Checking the piston ring end gap
(reference)
1. Level the piston ring a in the cylinder
with a piston crown.
2. Check the piston ring end gap a at the
specified measuring point b.
a
Crankcase
b
B
T
B
b
a
7-54
0
1
2
3
4
5
6
7
8
9
10
A