Yamaha F90D - Checking the Piston Ring Grooves; Checking the Piston Ring Side Clearance

6D81G11
5-42
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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.
Piston ring end gap
d
:
Top ring:
0.15–0.30 mm
(0.0059–0.0118 in)
Second ring:
0.70–0.90 mm
(0.0276–0.0354 in)
Oil ring:
0.20–0.70 mm
(0.0079–0.0276 in)
Measuring point
e
: 20 mm (0.8 in)
Piston ring groove:
Top ring
a
:
1.23–1.25 mm (0.048–0.049 in)
Second ring
b
:
1.52–1.54 mm (0.060–0.061 in)
Oil ring
c
:
2.51–2.53 mm (0.099–0.100 in)
S63P5720
a
b
c
Piston ring side clearance:
Top ring
a
:
0.04–0.08 mm
(0.0016–0.0031 in)
Second ring
b
:
0.03–0.07 mm
(0.0012–0.0028 in)
Oil ring
c
:
0.03–0.15 mm
(0.0012–0.0059 in)
S63P5730
a
b
c
Cylinder block