Arctic Cat ZR 120 Service Manual page 17

Measuring Camshaft End Running
Surfaces
1. Using an outside micrometer, measure the running
surfaces of each end of the camshaft. The mea-
surement should be at least 0.592".
2. Inspect the camshaft bosses of the crankcase and
crankcase cover for cracks, discoloration, and
wear.
PISTON ASSEMBLY
 NOTE: Oversized pistons are available allowing the
cylinder to be bored oversized.
 NOTE: Whenever a piston, rings, or pins are out of tol-
erance, they must be replaced.
Cleaning/Inspecting Piston
1. Using a non-metallic carbon removal tool, remove
any carbon buildup from the dome of the piston.
2. Inspect the piston for cracks in the piston pin,
dome, and skirt areas.
3. Inspect the piston for seizure marks or scuffing.
 NOTE: If seizure marks or scuffing is detected, the
piston must be replaced.
4. Inspect the perimeter of each piston for signs of
excessive "blowby." Excessive "blowby" indicates
worn piston rings or an out-of-round cylinder.
14
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 dome
of the piston while rotating it out of the groove.
 NOTE: Note the location of each ring for proper instal-
lation. When installing new rings, install as a complete
set only.
Cleaning/Inspecting Piston Rings
 NOTE: Make a ring-groove cleaning tool by taking an
IO088
old piston ring and snapping it into two pieces; then
grind the end of the old ring to a 45° angle and to a
sharp edge.
Using a ring-groove cleaning tool, clean carbon from the
ring-grooves. Be sure to position the ring with its tapered
side up.
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.
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.
 NOTE: When measuring a piston ring, it should be
placed into the area of the cylinder where wear is least
IO089
(the area is about 0.12" from the upper or lower edge of
the cylinder).
2. Using a feeler gauge, measure each piston-ring
end gap. Acceptable ring end gap must be within
0.008-0.016" (1st and 2nd rings) or within 0.0079-
0.0157" (oil ring).
CAUTION
IO083