Yamaha WR250FM Bicycle User Manual


 
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ENG
CYLINDER AND PISTON
Cylinder bore C
77.00 ~ 77.01 mm
(3.0315 ~ 3.0319 in)
Taper limit T 0.05 mm (0.002 in)
Out of round R 0.05 mm (0.002 in)
C = Maximum D
T = (Maximum D
1
or D
2
)
(Maximum D
5
or D
6
)
R = (Maximum D
1
, D
3
or D
5
)
(Minimum D
2
, D
4
or D
6
)
If out of specification, replace the cylinder,
and replace the piston and piston rings as
set.
2nd step:
Measure the piston skirt diameter P with
a micrometer.
a
8 mm (0.31 in) from the piston bottom edge
Piston size P
Standard
76.955 ~ 76.970 mm
(3.0297 ~ 3.0303 in)
If out of specification, replace the piston
and piston rings as a set.
3rd step:
Calculate the piston-to-cylinder clearance
with following formula:
Piston-to-cylinder clearance =
Cylinder bore C
Piston skirt diameter P
Piston-to-cylinder clearance:
0.040 ~ 0.065 mm
(0.0016 ~ 0.0026 in)
<Limit>: 0.1 mm (0.004 in)
If out of specification, replace the cylinder,
and replace the piston and piston rings as
set.