Removing The Piston; Checking The Cylinder And Piston - Yamaha YZF-R125 Service Manual

YamahaR125.COM
EAS24380

REMOVING THE PISTON

1. Remove:
• Piston pin clips "1"
• Piston pin "2"
• Piston "3"
ECA13810
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 prevent
the piston pin clip from falling into the crank-
case.
• Before removing the piston pin, deburr the pis-
ton pin clip groove and the piston pin bore ar-
ea. 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
Piston pin puller
YU-01304
2
3
2. Remove:
• Top ring
• 2nd ring
• Oil ring
1
CYLINDER AND PISTON
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.
EAS24390

CHECKING THE CYLINDER AND PISTON

1. Check:
• Piston wall
• Cylinder wall
Vertical scratches → Replace the cylinder,
and replace the piston and piston rings as a
set.
2. Measure:
• Piston-to-cylinder clearance
M MMM M MMM M M MMM
a. Measure cylinder bore "C" with the cylinder
bore gauge.
NOTE:
Measure cylinder bore "C" by taking side-to-side
and front-to-back measurements of the cylinder.
Then, find the average of the measurements.
Bore
52.000–52.010 mm (2.0472–
2.0476 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.005 mm (0.0002 in)
5-25
M M MMM M M MMM M M MMM M MMM