Arctic Cat Sno Pro 120 Service Manual page 104

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.
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.
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.
 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
 NOTE: The coolant temperature sensor must be
removed for this procedure.
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.
2-84
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.
AN135
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.
 NOTE: At this point, install the coolant temperature
sensor (threads coated with white Loctite #575) and
tighten to 18 ft-lb.
CRANKSHAFT
 NOTE: If any servicing of the connecting rods, cen-
ter bearings, or oil-injection pump drive gear is nec-
essary, Arctic Cat recommends the crankshaft be
taken to a qualified machine shop for that service.
1. Wash the crankshaft with bearings in parts-cleaning
solvent.
2. Inspect the bearings for wear, scoring, scuffing, dam-
age, or discoloration. Rotate the bearings. Bearings
must rotate freely and must not bind or feel rough. If
any abnormal condition is noted, replace the bearing.
CAUTION
CM160