Yamaha YFM250XL(C) Service Manual page 133

INSPECTION AND REPAIR
Oil control ring
Expander spacer of bottom ring (oil con-
trol ring) is color-coded to identify sizes.
Size
Oversize 2
Oversize 4
Piston pin
1.Inspect:
Piston pin
Blue discoloration/Grooves → Replace
then inspect lubrication system.
2.Measure:
Outside diameter a (piston pin)
Out of specification → Replace.
Outside diameter (piston pin):
15.991 ~ 16.000 mm
(0.6296 ~ 0.6299 in)
3.Measure:
Piston pin bore inside diameter b (piston)
Out of specification → Replace.
Piston pin bore inside diameter
(piston):
16.002 ~ 16.013 mm
(0.63 ~ 0.6304 in)
4.Measure:
Piston pin-to-piston clearance
Out of specification → Replace piston.
Piston pin-to-piston clearance =
Bore size (piston) b –
Outside diameter (piston pin) a
Piston pin-to-piston clearance:
0.002 ~ 0.022 mm
(0.0001 ~ 0.0009 in)
<Limit> 0.07 mm (0.003 in)
4 - 35
ENG
Color
Blue
Yellow
4