Yamaha MTN850-A 2017, Service Manual, Page: 297 / 560

CONNECTING RODS AND PISTONS
5-62
EAS30745
REMOVING THE CONNECTING RODS AND
PISTONS
The following procedure applies to all of the con-
necting rods and pistons.
1. Remove:
• Connecting rod cap “1”
•
Connecting rod
• Big end bearings
TIP
•
Identify the position of each big end bearing so
that it can be reinstalled in its original place.
•
After removing the connecting rods and con-
necting rod caps, care should be taken not to
damage the mating surfaces of the connecting
rods and connecting rod caps.
2. Remove:
• Piston pin clips “1”
•
Piston pin “2”
• Piston “3”
NOTICE
ECA13810
Do not use a hammer to drive the piston pin
out.
TIP
•
For reference during installation, put identifica-
tion marks on the piston crown.
•
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”.
3. 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.
EAS30747
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
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure cylinder bore “C” with the cylinder
bore gauge.
Piston pin puller set
90890-01304
Piston pin puller
YU-01304
1
1
2
3