Yamaha YFM250RX 2008 Service Manual page 151

CYLINDER AND PISTON
2. Install:
• Piston ring
(into the cylinder)
NOTE: NOTE:
Level the piston ring into the cylinder with the
piston crown.
40 mm (1.476 in)
3. Measure:
• Piston ring end gap
Out of specification → Replace the piston
ring.
NOTE: 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.
Piston ring
Top ring
End gap (installed)
0.19 ~ 0.31 mm
(0.007 ~ 0.012 in)
Limit
0.56 mm (0.022 in)
2nd ring
End gap (installed)
0.30 ~ 0.45 mm
(0.012 ~ 0.018 in)
Limit
0.80 mm (0.032 in)
Oil ring
End gap (installed)
0.10 ~ 0.35 mm
(0.004 ~ 0.014 in)
4-35
ENG