Removing The Piston; Checking The Cylinder And Piston - Yamaha 2010 XMAX YP125R Service Manual

EAS24380

REMOVING THE PISTON

1. Remove:
• Piston pin clips "1"
• Piston pin "2"
• Piston "3"
ECA13810
NOTICE
Do not use a hammer to drive the piston pin
out.
TIP
• Before removing the piston pin clips, cover the
crankcase opening with a clean rag to prevent
them from falling into the crankcase.
• 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. Remove:
• Top ring
• 2nd ring
• Oil ring
CYLINDER AND PISTON (YP250R)
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.
EAS24390

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
M MMM M MMM M M MMM
a. Measure cylinder bore "C" with the cylinder
bore gauge.
TIP
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
69.000–69.005 mm (2.7165–
2.7167 in)
Taper limit
0.030 mm (0.0012 in)
Out of round limit
0.030 mm (0.0012 in)
"C" = maximum of D
"T" = maximum of D
or D
6
"R" = maximum of D
D , D or D
2 4 6
5-85
M M MMM M M MMM M
–D
1 2
or D - maximum of D
1 2
, D or D - minimum of
1 3 5
M MMM M MMM
5