Yamaha XT250X 2008, Руководство по обслуживанию, Страница: 173 / 282

CYLINDER AND PISTON
5-27
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.
f. If out of specification, rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
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EAS24430
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 clearance,
eliminate any carbon deposits from the piston
ring grooves and piston rings.
2. Install:
●
Piston ring
(into the cylinder)
NOTE:
Level the piston ring into the cylinder with the
piston crown.
3. Measure:
●
Piston ring end gap
Out of specification
→
Replace the piston
ring.
NOTE:
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.
a. Piston skirt diameter
b. 11 mm (0.43 in) from the bottom edge of the pis-
ton
Diameter D
73.983
–
73.998 mm
(2.9127
–
2.9133 in)
Piston-to-cylinder clearance =
Cylinder bore “C” -
Piston skirt diameter “D”
Piston-to-cylinder clearance
0.010
–
0.025 mm (0.0004
–
0.0010
in)
Limit
0.15 mm (0.0059 in)
Piston ring side clearance
Top ring
Ring side clearance
0.030
–
0.065 mm (0.0012
–
0.0026
in)
Limit
0.115 mm (0.0045 in)
2nd ring
Ring side clearance
0.020
–
0.055 mm (0.0008
–
0.0022
in)
Limit
0.115 mm (0.0045 in)
a. 40 mm (1.57 in)
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