Checking The Piston Rings - Yamaha 2010 XMAX YP125R Service Manual

b. If out of specification, rebore or 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 mm (0.20 in) from the bottom edge of the
piston
Piston
Diameter D
68.965–68.980 mm (2.7152–
2.7157 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
0.020–0.040 mm (0.0008–0.0016
in)
Limit
0.15 mm (0.0059 in)
f. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
L LLL L LLL L L LLL L L LLL L L LLL L L LLL L
CYLINDER AND PISTON (YP250R)
EAS24430

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 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. 5 mm (0.20 in)
5-86
Top ring
Ring side clearance
0.040–0.080 mm (0.0016–
0.0031 in)
Limit
0.130 mm (0.0051 in)
2nd ring
Ring side clearance
0.030–0.070 mm (0.0012–
0.0028 in)
Limit
0.130 mm (0.0051 in)