Arctic Cat Sno Pro 120, Service Manual

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MD2491
4. Place the cylinder head on a Surface Plate covered
with #400 grit wet-or-dry sandpaper. Using light
pressure, move each cylinder head in a figure eight
motion. Inspect the sealing surface for any indication
of high spots. A high spot can be noted by a bright
metallic finish. Correct any high spots before assem-
bly by continuing to move the cylinder head in a fig-
ure eight motion until a uniform bright metallic
finish is attained.
MD2492
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 a 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 and reed valves after
honing using detergent soap and hot water and dry
with compressed 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. 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. If
scuffing or seizure marks are too deep, 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.
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 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.