Checking The Piston Rings - Yamaha YJ50RN Service Manual

CYLINDER HEAD, CYLINDER AND PISTON
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 "P" with the
micrometer.
a 5 mm (0.20 in) from the bottom edge of the pis-
ton
Standard
Oversize 1
Oversize 2
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 "P"
Piston-to-cylinder clearance
0.036 ~ 0.048 mm
(0.0014 ~ 0.0019 in)
<Limit>: 0.1 mm (0.0039 in)
f. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
▲ ▲▲▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲
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.
5 - 8
ENG
Piston size "P"
39.952 ~ 39.969 mm
(1.5729 ~ 1.5736 in)
40.25 mm (1.58 in)
40.5 mm (1.59 in)
▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲▲▲
5