Arctic Cat Sno Pro 120, Service Manual

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2-101
2
CYLINDERS
1. Using a non-metallic carbon removal tool, remove
carbon buildup from the exhaust ports.
2. Wash the cylinders in parts-cleaning solvent.
3. Inspect the cylinders for pitting, scoring, scuffing,
and corrosion. If marks are found, repair the surface
with the Ball Hone and honing oil.

NOTE: To produce the proper 45° crosshatch pat-
tern, maintain a low drill RPM. If honing oil is not
available, use a lightweight, petroleum-based oil.
Thoroughly clean the cylinders after honing using
detergent soap and hot water and dry with com-
pressed air; then immediately apply oil to the cylinder
bores. If a bore is severely damaged or gouged, the
cylinder must be replaced.
4. Place the head surface of each cylinder on the sur-
face plate covered with #400 grit wet-or-dry sandpa-
per. Using light pressure, move each cylinder in a
figure eight motion. Inspect the surface for any indi-
cation of high spots. A high spot can be noted by a
bright metallic finish. Correct any high spots before
assembly by continuing to move the cylinder in a fig-
ure eight motion until a uniform bright metallic fin-
ish is attained.
PISTON ASSEMBLY
1. Using a non-metallic carbon removal tool, remove
the carbon buildup from the dome of each piston.
2. Snap an old piston ring 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 car-
bon from the ring-grooves. Be sure to position 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.

NOTE: If synthetic oil is being used, a certain
amount of “blowby” may be visible under normal use.
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.
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
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.