Checking The Piston Rings - Yamaha YXR70FX Service Manual

CYLINDER AND PISTON
f. If out of specification, replace the cylinder,
and the piston and piston rings as a set.
L LLL L LLL L
EBS00250

CHECKING THE PISTON RINGS

1. Measure:
• piston ring side clearance
Out of specification → Replace the piston
and piston rings as a set.
TIP:
_
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the
piston ring grooves and piston rings.
Piston ring side clearance
Top ring
0.030 ~ 0.070 mm
(0.0012 ~ 0.0028 in)
<Limit>: 0.12 mm (0.0047 in)
2nd ring
0.030 ~ 0.070 mm
(0.0012 ~ 0.0028 in)
<Limit>: 0.13 mm (0.0051 in)
2. Install:
• piston ring
(into the cylinder)
TIP:
_
Level the piston ring into the cylinder with the
piston crown.
a 50 mm (1.97 in)
3. Measure:
• piston ring end gap
Out of specification → Replace the piston
ring.
TIP:
_
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 - 39
ENG
L LLL L L LLL L L LLL L L LLL L LLL