Yamaha TT-R90(R) Owner's Service Manual page 190

CYLINDER AND PISTON
REMOVAL POINTS
Piston
1. Remove:
Piston pin clips 1
G
Piston pin 2
G
Piston 3
G
NOTE:
Before removing the piston pin clip, cover the
G
crankcase opening with a clean towel or rag
to prevent the clip from falling into the crank-
case cavity.
Before removing each piston pin, deburr the
G
clip groove and pin hole 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:
YU-1304/90890-01304
Piston ring
1. Remove:
Piston rings
G
NOTE:
Spread the end gaps apart while at the same
time lifting the piston ring over the top of the
piston crown, as shown in the illustration.
INSPECTION
Cylinder and piston
1. Inspect:
Cylinder and piston walls
G
Vertical scratches → Replace cylinder
and piston.
2. Measure:
Piston-to-cylinder clearance
G
Measurement steps:
1st step:
Measure the cylinder bore "C" with a cylin-
G
der bore gauge.
NOTE:
Measure the cylinder bore "C" in parallel to
and at right angles to the crankshaft. Then,
find the average of the measurements.
4 - 22
ENG