Checking The Piston Rings - Yamaha WR125R 2009 Service Manual

"C" = maximum of D
"T" = maximum of D
or D
6
"R" = maximum of D
D , D or D
2 4 6
b. If out of specification, replace the cylinder,
and replace the piston and piston rings as a
set.
c. Measure piston skirt diameter D "a" with the
micrometer.
b. 5.0 mm (0.20 in) from the bottom edge of the
piston
Piston
Diameter D
51.962–51.985 mm (2.0457–
2.0466 in)
d. If out of specification, replace the piston and
piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
• Piston-to-cylinder clearance =
Cylinder bore "C" -
Piston skirt diameter "D"
Piston-to-cylinder clearance
0.015–0.048 mm (0.0006–0.0019
in)
Limit
0.15 mm (0.0059 in)
f. If out of specification, replace the cylinder,
and replace the piston and piston rings as a
set.
L LLL L LLL L L LLL L
–D
1 2
or D - maximum of D
1 2
, D or D - minimum of
1 3 5
L LLL L L LLL L L LLL L
CYLINDER AND PISTON
EAS24430

CHECKING THE PISTON RINGS

1. Measure:
5
• Piston ring side clearance
Out of specification → Replace the piston
and piston rings as a set.
TIP
Before measuring the piston ring side clearance,
eliminate any carbon deposits from the piston
ring grooves and piston rings.
Piston ring
2. Install:
• Piston ring
(into the cylinder)
TIP
Level the piston ring into the cylinder with the
piston crown.
LLL
a. 40 mm (1.57 in)
5-26
Top ring
Ring side clearance
0.030–0.065 mm (0.0012–
0.0026 in)
Limit
0.100 mm (0.0039 in)
2nd ring
Ring side clearance
0.020–0.055 mm (0.0008–
0.0022 in)
Limit
0.100 mm (0.0039 in)