Checking The Piston Diameter; Checking The Cylinder Bore; Checking The Piston Clearance; Checking The Piston Ring - Yamaha F30A Service Manual

POWR

Checking the piston diameter

1. Measure the piston diameter a at the
specified measuring point b. Replace if
out of specification.
Piston diameter a:
64.950–64.965 mm
(2.5571–2.5577 in)
Measuring point b:
2.0 mm (0.08 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 in 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 60 mm (2.4 in)
5-43
Power unit
–D ) at
1 6
, D ), which is parallel
3 5
D
1
d
D
3
e
D
5
S69J5B70
Cylinder bore (D
64.985–65.015 mm
(2.5585–2.5596 in)

Checking the piston clearance

1. Check the piston clearances if replacing
the pistons, piston ring sets, cylinder
block, or all parts.
NOTE:
The figures are for reference only. Depend-
ing on how the parts are assembled, the
actual measurements may not be within the
specified ranges.
Piston clearance (reference data):
0.035–0.065 mm
(0.0014–0.0026 in)

Checking the piston ring

1. Measure the piston ring dimensions B
and T. Replace the piston ring set if out
of specification.
,
2
–D ):
1 6
67C3K11