Yamaha RAPTOR YFM125RA, Service Manual, Page: 190 / 300

CYLINDER AND PISTON
5-27
EAS24380
REMOVING THE PISTON
1. Remove:
• Piston pin clips “1”
• Piston pin “2”
• Piston “3”
ECA13810
Do not use a hammer to drive the piston
pin out.
TIP
• 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 “4”.
2. Remove:
• Top ring
• 2nd ring
• Oil ring
TIP
When removing a piston ring, open the end
gap with your fingers and lift the other side of
the ring over the piston crown.
EAS2PA1503
CHECKING THE TIMING CHAIN GUIDE
1. Check:
• Timing chain guide (exhaust side)
Damage/wear
→
Replace.
EAS24400
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
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure cylinder bore “C” with the cylinder
bore gauge “1”.
TIP
Measure cylinder bore “C” by taking side-to-
side and front-to-back measurements of the
cylinder. Then, find the average of the mea-
surements.
Piston pin puller set
90890-01304
Piston pin puller
YU-01304
Cylinder bore “C”
54.024–54.056 mm (2.1269–
2.1282 in)
Wear limit
54.156 mm (2.1321 in)
“C” = (X+Y)/2