Yamaha YFM90RA Model Vehicle User Manual


 
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ENG
CYLINDER AND PISTON
EBS00247
REMOVING THE PISTON
1. Remove:
piston pin clips
piston pin
piston
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 crankcase.
Before removing each piston pin, deburr the
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 .
NOTICE
Do not use a hammer to drive the piston
pin out.
2. Remove:
piston rings
TIP
Spread the end gaps apart while at the same
time lifting the piston ring over the top of the
piston crown.
Piston pin puller set
P/N. YU-01304, 90890-01304
EBS00249
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 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.
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