Yamaha TZ250M, Owner'S Service Manual

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Repairing steps:
• Remove the piston ring.
• Chamfer the piston ring groove at its edge
a
where the piston ring tends to stick,
using a triangle oil stone
2
with the engine
mixing oil.
NOTE:
• Set the triangle oil stone to the piston ring
groove to form an angle of 45°. Do the
chamfering with force applied to this edge.
• Chamfer until the piston ring moves
smoothly.
CC CAUTION:
Do not over-chamfer.
CYLINDER HEAD, CYLINDER AND PISTON
4-22
3. Inspect:
• Travel distance for cylinder
3,000 km (1,800 miles) or more
≥
Replace.
EC474313
Piston
1. Inspect:
• Piston crown
Damage and crack due to detonation
≥
Replace.
• Piston pin hole
Crack
≥
Replace.
• Contact with cylinder
Excessive scuffing, score
a
≥
Use
#240~320 grit wet sandpaper in a criss-
cross manner
b
.
• Heat discoloration
≥
Replace.
2. Inspect:
• Travel distance for piston
500 km (300 miles) or more
≥
Replace.
3. Check:
• Piston ring free movement
Mechanical stick
≥
Repair.
Install the piston ring
1
to the piston, and
check for free movement.
ENG