Arctic Cat Sno Pro 120 2011, Service Manual

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PISTON ASSEMBLY
1. Using a non-metallic carbon removal tool, remove
the carbon buildup from the dome of each piston.
2. 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. Using the sharpened ring as a tool,
clean carbon from the ring-grooves. Be sure to posi-
tion the ring with its tapered side up.
3. Inspect each piston for cracks in the piston pin and
skirt areas.
4. Inspect each piston for seizure marks or scuffing.
Repair with #400 grit wet-or-dry sandpaper and
water or honing oil.
AN135

NOTE: If scuffing or seizure marks are too deep to
correct with the sandpaper, it will be necessary to
replace the piston.
5. Inspect the perimeter of each piston for signs of
excessive “blowby.” Excessive “blowby” indicates
worn piston rings or an out-of-round cylinder.
CRANKCASE
1. Wash the crankcase halves in parts-cleaning solvent.

NOTE: Before washing the crankcase halves, make
sure the four bearing dowel pins have been removed
and accounted for.
2. Inspect the crankcase halves for scoring, pitting,
scuffing, or any imperfections in the casting.
3. Inspect all threaded areas for damaged or stripped
threads.
4. Inspect the bearing areas for cracks or excessive
bearing movement. If evidence of excessive bearing
movement is noted, the crankcase must be replaced.
5. Inspect the bearing dowel pins for wear.
6. Inspect the sealing surfaces of the crankcase halves
for trueness by placing each crankcase half on the
surface plate covered with #400 grit wet-or-dry sand-
paper. Using light pressure, move each half in a fig-
ure eight motion. Inspect the sealing surfaces for any
indication of high spots. A high spot can be noted by
a bright metallic finish. Correct any high spots by
continuing to move the half in a figure eight motion
until a uniform bright metallic finish is attained.

NOTE: Care must be taken not to remove an exces-
sive amount of aluminum, or the crankcase must be
replaced. If excessive aluminum is removed, too
much pre-load will be exerted on the crankshaft bear-
ings when assembled.
MD0200A
INSULATOR PLATES
1. Inspect for cracks, scoring, pitting, imperfections, or
warping.
2. Inspect the sealing surfaces for trueness by placing
each on the surface plate covered with #400 grit wet-
or-dry sandpaper. Using light pressure, move both
sides in a figure eight motion. Inspect the sealing
surface for any indication of high spots or warping.
Correct high spots by continuing to move each side
in a figure eight motion. Warped components must
be replaced.

NOTE: In order to inspect insulator plate trueness, it
will be necessary to remove the studs.
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.
CAUTION
Water or parts-cleaning solvent must be used in con-
junction with the wet-or-dry sandpaper or damage to
the sealing surface may result.
CAUTION
Water or parts-cleaning solvent must be used in con-
junction with the wet-or-dry sandpaper or damage to
the sealing surfaces may result.
Manual
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