Yamaha TZ125M1 Owner's Service Manual page 109

CYLINDER HEAD, CYLINDER AND PISTON
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.
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.
C C CAUTION:
Do not over-chamfer.
EC474402
Piston pin and small end bearing
1. Inspect:
• Piston pin
• Small end bearing
Signs of heat discoloration ≥ Replace.
4-21
ENG