Checking The Cylinder Bore; Checking The Piston Clearance; Checking The Piston Rings - Yamaha F15B Service Manual

POWR

Checking the cylinder bore

1. Measure the cylinder bore (D
measuring points a, b, and c, and in
direction d (D
, D
1
to the crankshaft, and direction e (D
D , D ), which is at a right angle to the
4 6
crankshaft.
D
2
D
4
D
6
a 10 mm (0.39 in)
b 40 mm (1.57 in)
c 70 mm (2.76 in)
Cylinder bore (D
59.000–59.015 mm
(2.3288–2.3234 in)
2. Calculate the taper limit. Replace or
rebore the cylinder block if out of specifi-
cation.
Taper limit:
(direction d)
D –D
1 5
(direction e)
D –D
2 6
0.08 mm (0.0032 in)
3. Calculate the out-of-round limit. Replace
or rebore the cylinder block if out of spec-
ification.
Out-of-round limit:
(direction a)
D –D
2 1
(direction c)
D –D
6 5
0.05 mm (0.0020 in)
5-39
Power unit
–D ) at
1 6
, D ), which is parallel
3 5
D
1
D
3
D
5
6D451070
–D ):
1 6

Checking the piston clearance

1. Rebore the cylinder or replace the piston
and piston rings as a set, or the cylinder
block, or all parts if out of specification.
,
2
Piston clearance:
0.035–0.065 mm
(0.0014–0.0026 in)

Checking the piston rings

1. Check the piston ring dimensions of B
and T. Replace if out of specification.
a
T
c
Piston ring dimensions:
Top ring a:
Second ring b:
Oil ring c:
b
B
B
T
B: 1.17–1.19 mm
(0.0461–0.0469 in)
T: 2.00–2.20 mm
(0.0787–0.0866 in)
B: 1.47–1.49 mm
(0.0579–0.0590 in)
T: 2.50–2.70 mm
(0.0984–0.1063 in)
B: 2.31–2.51 mm
(0.0909–0.0988 in)
T: 2.30–2.60 mm
(0.0906–0.1024 in)
B
T
6D451200
6D45F11