Yamaha YZ250, Owner'S Service Manual, Page: 264 / 596

4-23
ENG
CYLINDER HEAD, CYLINDER AND PISTON
3. Measure:
9 Piston skirt diameter
Use micrometer
1
.
Measure the specific distance
b
from the
stepped surface
a
on inside of the piston.
Out of specification
→
Replace.
EC474402
Piston pin and small end bearing
1. Inspect:
9 Piston pin
9
Small end bearing
Signs of heat discoloration
→
Replace.
2. Measure:
9
Piston pin outside diameter
Use micrometer
1
.
Out of limit
→
Replace.
3. Check:
9 Free play (when the piston pin
1
is in
place in the piston
2
)
There should be no noticeable for the play.
Free play exists
→
Replace piston pin
and/or piston.
4. Install:
9
Small end bearing
9 Piston pin
Into the small end of connecting rod.
17.5 mm 66.352~66.367 mm
(0.69 in) (2.6120~2.6129 in)
Distance
b b
Piston dia.
Piston pin outside diameter:
Standard <Limit>
17.995~18.000 mm 17.975 mm
(0.7085~0.7087 in) (0.7077 in)
1P8-9-32-4a 4/10/06 1:53 PM Page 46