Yamaha F225F, Service Manual

Page: 362 / 576

7-79
Power unit
POWR
Checking the piston ring end gap
1. Level the piston ring
a
in the cylinder
using a piston crown at the specified
measuring point
a
.
2. Measure the piston ring end gap
b
.
Checking the piston ring groove
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.
Checking the piston pin boss inside
diameter
1. Measure the piston pin boss inside diam-
eter.
Piston ring dimension:
Top ring
a
:
B: 1.200 mm (0.0472 in)
T: 2.800–3.000 mm (0.1102–0.1181 in)
2nd ring
b
:
B: 1.170–1.190 mm (0.0461–0.0469 in)
T: 3.800–4.000 mm (0.1496–0.1575 in)
Oil ring
c
:
B: 2.400–2.470 mm (0.0945–0.0972 in)
T: 2.350–2.750 mm (0.0925–0.1083 in)
Measuring point
a
(reference data):
20.0 mm (0.8 in)
Piston ring end gap
b
(reference data):
Top ring:
0.200–0.300 mm (0.0079–0.0118 in)
2nd ring:
0.600–0.750 mm (0.0236–0.0295 in)
Oil ring:
0.150–0.600 mm (0.0059–0.0236 in)
a
b
a
Piston ring groove:
Top ring
a
:
1.230–1.250 mm (0.0484–0.0492 in)
2nd ring
b
:
1.220–1.240 mm (0.0480–0.0488 in)
Oil ring
c
:
2.510–2.530 mm (0.0988–0.0996 in)
Piston ring side clearance:
Top ring
a
:
0.030–0.050 mm (0.0012–0.0020 in)
2nd ring
b
:
0.030–0.070 mm (0.0012–0.0028 in)
Oil ring
c
:
0.040–0.130 mm (0.0016–0.0051 in)
a
b
c
a
b
c