Removing The Piston; Checking The Cylinder And Piston - Yamaha YFM250RX 2008 Service Manual

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CYLINDER AND PISTON

REMOVING THE PISTON

1. Remove:
• Piston pin clips
• Piston pin
• Piston
NOTE: NOTE:
• Before removing the piston pin clip, cover the
crankcase opening with a clean rag to pre-
vent the piston pin clip from falling into the
crankcase.
• Before removing each piston pin, deburr the
clip groove and pin hole area. If the piston pin
groove is deburred and the piston pin is still
difficult to remove, use the piston pin puller
.
Piston pin puller set
90890-01304
Piston pin puller
YU-01304
CAUTION:
Do not use a hammer to drive the piston
pin out.
2. Remove:
• Top ring
• 2nd ring
• Oil ring
NOTE: NOTE:
When removing a piston ring, open the end
gap with your fingers and lift the other side of
the ring over the piston crown.

CHECKING THE CYLINDER AND PISTON

1. Check:
• Piston wall
• Cylinder wall
Vertical scratches → Rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
2. Measure:
• Piston-to-cylinder clearance
4-32
ENG