Removing The Piston; Checking The Cylinder And Piston - Yamaha WR450FB 2012 Owner's 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 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
piston pin clip's groove and the piston's pin
bore area. If the piston pin groove is deburred
and the piston pin is still difficult to remove,
use the piston pin puller set "4".
Piston pin puller set
90890-01304
YU-01304
1
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.
CYLINDER AND PISTON
EAS24390

CHECKING THE CYLINDER AND PISTON

1. Check:
• Piston wall (Sidewall)
• Cylinder wall
Vertical scratches
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.
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.
Bore
95.000–95.010 mm (3.7402–
3.7405 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.050 mm (0.0020 in)
"C" = maximum of D
"T" = (maximum of D
or D )
6
Out of round limit = maximum of D
- maximum of D
2
6-27
Replace the cylinder,
–D
1 6
or D ) - (maximum of D
1 2
, D or D
1 3
, D or D
4 6
5
5