Checking The Piston Rings - Yamaha YZ450F Owner's Service Manual

b. If out of specification, rebore or replace the
cylinder, and replace the piston and the pis-
ton rings as a set.
c. Measure the piston outside diameter "a" at
the measuring point (from piston skirt bot-
tom) "b" with the micrometer.
Diameter
96.955–96.970 mm (3.8171–
3.8177 in)
Measuring point (from piston
skirt bottom)
9.0 mm (0.35 in)
b
d. If out of specification, replace the cylinder,
the piston, and the piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
Piston-to-cylinder clearance =
Cylinder bore - Piston diameter
Piston-to-cylinder clearance
0.030–0.055 mm (0.0012–0.0022
in)
Limit
0.15 mm (0.006 in)
f. If out of specification, replace the cylinder,
the piston, and the piston rings as a set.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EASB111228
a
CYLINDER AND PISTON

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.
Ring side clearance
Top ring
0.015–0.065 mm (0.0006–0.0026
in)
Limit
0.120 mm (0.0047 in)
2nd ring
0.020–0.060 mm (0.0008–0.0024
in)
Limit
0.120 mm (0.0047 in)
2. Install:
• Piston ring
TIP
Level the piston ring into the cylinder with the
piston.
a. 10 mm (0.39 in)
3. Measure:
• Piston ring end gap
Out of specification  Replace the piston
ring.
5-35