Yamaha MX250 - Page 78

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ENGINE
PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT
2.
Install:
• Piston ring
(into the cylinder)
TIP
Use the piston crown to level the piston ring near bottom of
cylinder “a”, where cylinder wear is lowest.
3.
Measure:
• Piston ring end gap
Out of specification  Replace the piston rings as a
set.
Piston ring
Top ring
Side clearance:
0.03–0.05 mm (0.0011–0.0019 in)
Limit:
0.10 mm (0.0039 in)
2nd ring
Side clearance:
0.02–0.04 mm (0.0007–0.0015 in)
Limit:
0.10 mm (0.0039 in)
a
b
b. Upper of cylinder
Top ring
End gap (installed):
0.20–0.35 mm (0.0079–0.0138 in)
Limit:
0.60 mm (0.0236 in)
2nd ring
End gap (installed):
0.20–0.35 mm (0.0079–0.0138 in)
Limit:
0.70 mm (0.0275 in)
Oil ring
End gap (installed):
0.20–0.70 mm (0.0079–0.0276 in)