Yamaha 2004 YP400, Service Manual, Page: 244 / 417

5 - 31
ENG
CYLINDER AND PISTON
EAS00253
REMOVING THE PISTON
1. Remove:
• piston pin clip
1
• piston pin
2
• piston
3
CAUTION:
_
Do not use a hammer to drive the piston
pin out.
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 the piston pin, deburr the
piston pin clip’s groove and the piston’s pin
bore area. If both areas are deburred and the
piston pin is still difficult to remove, remove it
with the piston pin puller set
4
.
Piston pin puller set
90890-01304, YU-01304
1
2
3
2. Remove:
• top ring
• 2nd ring
• oil ring
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.
EAS00255
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.