Yamaha F2.5C, Service Manual, Page: 100 / 184

POWR
Power unit
5-39
6D55F11
Checking the piston ring grooves
1. Measure the piston ring grooves.
Replace the piston if out of specification.
Checking the piston ring side
clearance
1. Measure the piston ring side clearance.
Replace the piston and piston rings as a
set if out of specification.
Checking the piston pin boss bore
1. Measure the piston pin boss bore.
Replace the piston if out of specification.
Checking the piston pin
1. Measure the piston pin diameter.
Replace if out of specification.
Piston ring groove:
Top ring
a
:
1.21–1.23 mm
(0.0476–0.0484 in)
2nd ring
b
:
1.51–1.53 mm
(0.0594–0.0602 in)
Oil ring
c
:
2.52–2.54 mm
(0.0992–0.1000 in)
Piston ring side clearance:
Top ring
a
:
0.02–0.06 mm
(0.0008–0.0024 in)
2nd ring
b
:
0.02–0.06 mm
(0.0008–0.0024 in)
Oil ring
c
:
0.04–0.18 mm
(0.0016–0.0070 in)
Piston pin boss bore:
15.974–15.985 mm
(0.6289–0.6293 in)
Piston pin diameter:
15.965–15.970 mm
(0.6285–0.6287 in)