Checking The Cylinder Bore; Checking The Piston Clearance; Checking The Piston Rings - Yamaha F150A Service Manual

Piston diameter a:
93.928–93.934 mm
(3.6979–3.6982 in)
Measuring point b:
5.0 mm (0.20 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
94.000–94.017 mm
(3.7008–3.7014 in)
2. Calculate the taper limit. Replace the cyl-
inder block if out of specification.
Taper limit:
(direction d)
D –D
1 5
(direction e)
D –D
2 6
0.08 mm (0.0032 in)
63P3F11
–D ) at
1 6
, D ), which is parallel
5
,
2
D
1
d
D
3
e
D
5
S69J5B70
–D ):
1 6
3. Calculate the out-of-round limit. Replace
the cylinder block if out of specification.
Out-of-round limit:
(measuring point a)
D –D
2 1
(measuring point c)
D –D
6 5
0.05 mm (0.0020 in)

Checking the piston clearance

1. Replace the piston and piston rings as a
set, or the cylinder block, or all parts if
out of specification.
Piston clearance:
0.075–0.080 mm
(0.0030–0.0031 in)

Checking the piston rings

1. Check the piston ring dimensions of B
and T. Replace if out of specification.
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)
Cylinder block
1
2
3
4
5
6
7
8
9
5-42