Yamaha F30A 2018, Service Manual

Page: 207 / 348

7-52
Cylinder block
Checking the piston clearance
1. Measure:
• Piston diameter
See “Checking the piston diameter” (7-51).
• Cylinder bore
See “Checking the cylinder bore” (7-51).
2. Calculate:
• Piston clearance
Out of specification

Replace the piston
or cylinder block.
Checking the piston ring
1. Measure:
• Piston ring dimensions B and T
Below specification

Replace.
Checking the piston ring end gap
1. Measure:
• Piston ring end gap
Above specification

Replace.
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a. Level the piston ring “1” in the cylinder us-
ing a piston crown at the specified measur-
ing point “a”.
Piston clearance = maximum cylin-
der bore – piston outside diameter
Piston clearance
0.035–0.065 mm (0.0014–
0.0026 in)
Limit
0.115 mm (0.0045 in)
a. Top ring
b. 2nd ring
c. Oil ring
T
B
T
T
B
B
a b
c
Piston ring dimensions
Top ring
Height (B)
1.170–1.190 mm (0.0461–
0.0469 in)
Width (T)
2.300–2.500 mm (0.0906–
0.0984 in)
2nd ring
Height (B)
1.470–1.490 mm (0.0579–
0.0587 in)
Width (T)
2.600–2.800 mm (0.1024–
0.1102 in)
Oil ring
Height (B)
2.360–2.480 mm (0.0929–
0.0976 in)
Width (T)
2.750 mm (0.1083 in)
Top ring
End gap
0.15–0.30 mm (0.0059–0.0118
in)
Limit
0.500 mm (0.0197 in)
2nd ring
End gap
0.30–0.50 mm (0.0118–0.0197
in)
Limit
0.700 mm (0.0276 in)
Oil ring
End gap
0.20–0.70 mm (0.0079–0.0276
in)