Removing The Piston; Checking The Cylinder And Piston - Yamaha R15 2022 Service Manual

EAS30289

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 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.
Piston pin replacer
YSST-207
(90890-01304)
2
3
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
1
EAS30291

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 cylin-
der 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 measurements.
Bore
58.000–58.010 mm (2.2835–
2.2839 in)
Wear limit
58.060 mm (2.2858 in)
Cylinder bore "C" = maximum of Diameter
Taper limit "T" = maximum of D
of D or D
5 6
Out of round limit "R" = maximum of D
maximum of D
2
G089000
b. If out of specification, replace the cylinder,
and replace the piston and piston rings as
a set.
c. Measure piston skirt diameter D "a" with
the micrometer.
5-28
ENG
or D - maximum
1 2
1
, D or D
4 6
, D or D -
3 5