Arctic Cat 2009 366 Service Manual page 41

PISTON ASSEMBLY
NOTE: Whenever a piston, rings, or pin are out of
tolerance, they must be replaced.
Cleaning/Inspecting Piston
1. Using a non-metallic carbon removal tool, remove
any carbon buildup from the top of the piston.
2. Inspect the piston for cracks in the piston pin,
boss, top, and skirt areas.
3. Inspect the piston for seizure marks or scuffing. If
piston is scored or galled, replace it with a new
one.
4. Inspect the perimeter of each piston for signs of
"blowby" indicated
"Blowby" is caused by worn piston rings, exces-
sive carbon in ring grooves, or an out-of-round
cylinder.
Removing Piston Rings
1. Starting with the top ring, slide one end of the ring
out of the ring-groove.
2. Remove each ring by working it toward the top of
the piston while rotating it out of the groove.
NOTE: If the existing rings will not be replaced
with new ones, note the location of each ring for
proper installation. When installing new rings,
install as a complete set only.
Cleaning/Inspecting Piston Rings
1. Take an old piston ring and snap it into two pieces;
then grind the end of the old ring to a 45° angle
and to a sharp edge.
2. Using the sharpened ring as a tool, clean carbon
from the ring grooves. Be sure to position the ring
with its tapered side up.
! CAUTION
Improper cleaning of the ring grooves by the use of
the wrong type of ring groove cleaner will result in
severe damage to the piston.
Back
by dark discoloration.
CC400D
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Measuring Piston-Ring End Gap
(Installed)
1. Place each piston ring in the wear portion of the
cylinder. Use the piston to position each ring
squarely in the cylinder.
2. Using a feeler gauge, measure each piston-ring
end gap. Acceptable ring end gap must be within
specifications.
Measuring Piston Pin, Connecting
Rod Small End, and Piston-Pin Bore
1. Measure the piston pin outside diameter at each
end and in the center. If measurement exceeds
specifications, the piston pin must be replaced.
2. Inspect and measure the connecting rod small end.
If the measurement exceeds specifications, the
connecting rod must be replaced (see Center
Crankcase Components in this section).
3. Insert an inside dial indicator into the piston-pin
bore. Take two measurements to ensure accuracy.
The diameter must not exceed specifications. If the
diameter exceeds specifications, the piston must
be replaced.
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CC995
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