Arctic Cat ZR 120 Service Manual page 18

Piston Ring/Groove Clearance
1. Using a thickness gauge, measure the side clear-
ances of the 1st and 2nd rings.
2. If the measurements are not within 0.0016-
0.0030" (1st ring) or 0.0008-0.0024" (2nd ring),
replace both piston and piston rings.
Measuring Piston Skirt/Cylinder
Clearance
1. Measure the cylinder front to back in six places
using a cylinder bore gauge. The amount of wear
is the difference between the largest and smallest
readings. If the determined wear exceeds the limit
indicated, bore to the next oversize by using a bor-
ing machine or replace the cylinder.
2. Measure the corresponding piston diameter at a
point 10 mm above the piston skirt at a right angle
to the piston-pin bore. Piston diameter must be at
least 2.205".
3. Piston skirt to cylinder clearance must be within
0.0006-0.0016".
4. If the piston/cylinder clearance exceeds the limit,
bore the cylinder and use an oversized piston or
replace both cylinder and piston.
Installing Piston Rings
1. Place the oil ring expander into the bottom groove
of the piston allowing the ends to contact each
other.
IO090
Never allow the ends of the oil ring expanders to over-
lap. This allows a loss of oil control and incorrect ten-
sion of the ring.
2. Place one end of the thin oil ring between the top
of the oil ring expander and the ring groove; then
wind the ring around the piston until the ring is
properly seated into the ringland of the piston.
Repeat this procedure for the lower thin oil ring.
3. Position the thin oil ring gaps 90° from the gap of
the oil ring expander and 180° from each other.
4. Install the middle and top compression ring with
the I.D. mark directed toward the dome of the pis-
ton.

NOTE: The top compression ring can be identified by
the chrome (silver) face of the ring.
Incorrect installation of the piston rings will result in
engine damage.
Measuring Piston Pin Diameter
1. Measure the piston pin diameter at each end and in
the center. If measurement is less than minimum
specifications, the piston pin must be replaced.
2. Piston pin diameter must be within 0.6297-0.6299".
GEN-0032
Measuring Piston Pin Bore Diameter
1. Insert an inside dial indicator into the piston-pin
bore. Take two measurements to ensure accuracy.
2. Piston pin bore must not exceed 0.433".
IO085
CAUTION
CAUTION
IO086
15