Yamaha XN125 2000, Service Manual

Page: 121 / 259

ENG
4-25
EAS00264
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 clearance,
remove any carbon deposits from the piston ring
grooves and piston rings.
Piston ring side clearance
Top ring
0.03 ~ 0.07 mm
<Limit>: 0.12 mm
2nd ring
0.02 ~ 0.06
<Limit>: 0.12 mm
2. Install:
• piston ring
(into the cylinder)
NOTE:
Level the piston ring into the cylinder with the
piston crown.
a 0.5 mm
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 excessive,
replace all three piston rings.
Piston ring end gap
Top ring
0.15 ~ 0.25 mm
<Limit>: 0.50 mm
2nd ring
0.15 ~ 0.30 mm
<Limit>: 0.65 mm
Oil ring
0.20 ~ 0.70 mm
CYLINDER AND PISTON
a