Yamaha F40B - Checking the Piston Ring End Gap; Checking the Piston Ring Groove

67C3K11 5-44
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Checking the piston ring end gap
1. Level the piston ring 1 in the cylinder
with a piston crown at the specified mea-
suring point a.
2. Measure the piston ring end gap b.
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.
Checking the piston ring groove
1. Measure the piston ring grooves.
Replace the piston if out of specification.
Piston ring dimensions:
Top ring a:
B: 1.17–1.19 mm
(0.0461–0.0469 in)
T: 2.30–2.50 mm
(0.0906–0.0984 in)
2nd ring b:
B: 1.47–1.49 mm
(0.0579–0.0587 in)
T: 2.60–2.80 mm
(0.1024–0.1102 in)
Oil ring c:
B: 2.36–2.48 mm
(0.0929–0.0976 in)
T: 2.75 mm (0.1083 in)
(reference data)
S67C5129
1
a
b
Piston ring end gap b (reference
data):
Top ring:
0.15–0.30 mm
(0.0059–0.0118 in)
2nd ring:
0.30–0.50 mm
(0.0118–0.0197 in)
Oil ring:
0.20–0.70 mm
(0.0079–0.0276 in)
Measuring point a (reference data):
20 mm (0.8 in)
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)
S67C5130
a
b
c
Cylinder block