Checking The Piston Diameter; Checking The Cylinder Bore; Checking The Piston Clearance; Checking The Piston Rings - Yamaha F50F Service Manual

POWR

Checking the piston diameter

1. Measure the piston outside diameter at
the specified measuring point. Replace if
out of specification.
Piston diameter a:
64.950–64.965 mm
(2.5571–2.5577 in)
Measuring point b:
5.0 mm (0.20 in) up from the
bottom of the piston skirt
Oversize piston diameter:
Oversize 1st:
65.200–65.215 mm
(2.5669–2.5675 in)
Oversize 2nd:
65.450–65.465 mm
(2.5768–2.5774 in)

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.
a
b
D
2
c
D
4
D
6
a 20 mm (0.8 in)
b 40 mm (1.6 in)
c 70 mm (2.8 in)
5-39
Power unit
–D ) at
1 6
, D ), which is parallel
3 5
D
1
d
D
3
e
D
5
S69J5B70
Cylinder bore (D
65.000–65.015 mm
(2.5591–2.5596 in)
2. Calculate the taper limit. Replace the cyl-
inder block if above specification.
Taper limit:
D
D
3. Calculate the out-of-round limit. Replace
the cylinder block if above specification.
Out-of-round limit:
D
D

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:
0.035–0.065 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.
,
2
–D ):
1 6
(direction d)
–D
1 5
(direction e)
–D
2 6
0.08 mm (0.0032 in)
(measuring point a)
–D
2 1
(measuring point c)
–D
6 5
0.05 mm (0.0020 in)
6C13G11