Removing The Piston; Checking The Cylinder And Piston - Yamaha SR400 2014 Service Manual

EAS24380

REMOVING THE PISTON

1. Remove:
• Piston pin clip "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 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
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
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the cylinder bore "C" with the cylin-
der bore gauge.
TIP
Measure the cylinder bore "C" by taking
3
side-to-side and front-to-back measurements of
the cylinder. Then, find the average of the mea-
surements.
2
1
"C" = maximum of D
Taper limit = maximum of D
mum of D
Out of round limit = maximum of D
minimum of D
5-24
CYLINDER AND PISTON
Bore
87.000–87.015 mm
(3.4252–3.4258 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.010 mm (0.0004 in)
–D
1 6
1
or D
5 6
, D or D
2 4 6
or D - maxi-
2
, D or D -
1 3 5