Yamaha YFM250XL(C) Service Manual page 132

4
INSPECTION AND REPAIR
Top
ring
2nd
ring
2.Position:
Piston ring
(into cylinder)
NOTE:
Insert the ring into the cylinder, and push it
approximately 20 mm (0.8 in) into the cylin-
der. Push the ring with the piston crown so
that the ring will be at a right angle to the
cylinder bore.
3.Measure:
End gap
Use a Feeler Gauge 1
Out of specification → Replace rings as set.
Top
ring
2nd
ring
Oil ring
NOTE:
You cannot measure end gap on expander
spacer of oil control ring. If oil control ring
rails show excessive gap, replace all three
rings.
Piston ring oversize
Top and 2nd piston ring
Oversize top and middle ring sizes are
stamped on top of ring.
Oversize 2
Oversize 4
4 - 34
ENG
Side clearance
Standard
0.12 mm
0.03 ~ 0.07 mm
(0.005 in)
(0.001 ~ 0.003 in)
0.12 mm
0.02 ~ 0.06 mm
(0.005 in)
(0.0008 ~ 0.0024 in)
End gap
Standard
0.4 mm
0.15 ~ 0.30 mm
(0.016 in)
(0.006 ~ 0.012 in)
0.4 mm
0.15 ~ 0.30 mm
(0.016 in)
(0.006 ~ 0.012 in)
0.2 ~ 0.7 mm
(0.008 ~ 0.028 in)
0.50 mm (0.0197 in)
1.00 mm (0.0394 in)
Limit
Limit
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