Checking The Piston Rings - Yamaha MIO Service Manual

a
CYLINDER AND PISTON
Piston-to-cylinder clearance
f. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
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EAS00263

CHECKING THE PISTON RINGS

1. Measure:
• piston ring side clearance
Out of specification → Replace the piston
and piston rings as a set.
NOTE:
_
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the
piston ring grooves and piston rings.
Piston ring side clearance
2. Install:
• piston ring
(into the cylinder)
NOTE:
_
Level the piston ring into the cylinder with the
piston crown.
a 5.0 mm (0.20 in)
3. Measure:
• piston ring end gap
Out of specification → Replace the piston
ring.
NOTE:
_
The oil ring expander spacer's end gap cannot
be measured. If the oil ring rail's gap is exces-
sive, replace all three piston rings.
4 - 35
ENG
0.020 ~ 0.035 mm
(0.0008 ~ 0.0014 in)
<Limit>: 0.15 mm (0.0059 in)
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Top ring
0.03 ~ 0.07 mm
(0.0012 ~ 0.0028 in)
<Limit>: 0.12 mm (0.0047 in)
2nd ring
0.02 ~ 0.06 mm
(0.0008 ~ 0.0024 in)
<Limit>: 0.12 mm (0.0047 in)
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