Arctic Cat M 8000, Service Manual

Page: 120 / 210

119
OPERATION
At idle and low speed operation, the exhaust valves are
held in the “low port” position by the return spring.
When engine RPM reaches a predetermined point, the
ECM will send a signal to the servomotor which cycles
and pulls the exhaust valves into the mid-point. At
another RPM, the ECM will send a signal to the servo-
motor which cycles and pulls the exhaust valves to the up
or “high port” position.
If the servomotor cycles the exhaust valves as explained
above, the exhaust valve circuit is operating satisfacto-
rily. If the servomotor makes no attempt to open the
valves or if the servomotor attempts to cycle the valves
three times (then stops working), a problem exists and it
must be corrected.
Servomotor Cycles Three Times
In this situation the ECM computer has been pro-
grammed with a voltage range (low and high) that the
servomotor must operate within. If the servomotor is put
under too much load, its resistance goes up and may
exceed the range upper limit. It will then stop and attempt
two more times. If the resistance still is too high, it shuts
down.
If the servomotor is commanded to move but the potenti-
ometer output voltage does not change, an error occurs
and the check engine light will flash a trouble code.
Improper servomotor position sensing is normally caused
by one or more of the following:
A. Incorrect exhaust valve cable length (too long or too
short).
B. Exhaust valve cable(s) sticking, broken, or discon-
nected at pulley.
C. Exhaust valves sticking.
D. Exhaust valve spring(s) weak or broken.
Check each of the above probable causes in the order
given to locate the problem of the servomotor cycling
three times in succession; then shutting down.
Check for correct exhaust valve cable length specifica-
tions for model being worked on in this section.
Servomotor Makes No Attempt To
Cycle
If when running the engine the servomotor makes no
attempt to operate, this is caused by one or more of the
following:
A. Bad connection from the wiring harness and connec-
tor from the lighting coil to the ECM, or from the
ECM to servomotor.
B. ECM output to servomotor is too low.
C. Servomotor failure.
D. Blown fuse.
E. Voltage Regulator/Rectifier.
 NOTE: For testing individual APV system compo-
nents, see the Electrical Systems section.
MAINTENANCE
The APV system requires only periodic cleaning and
cable adjustment. The cables should be checked every
2600 miles and adjusted as necessary.
CABLE ADJUSTMENT
Proper cable adjustment is critical to the operation of the
APV system. To check the cable adjustment, use the fol-
lowing procedure.
1. Using a small needle-nose pliers, remove the servo-
motor cable holder.
PC187A
2. Pull the cable housings down and out of the servo-
motor; then slide each cable end out of the slot of the
pulley.
PC134
 NOTE: Ensure the exhaust valves are free to move.
3. While holding the cable housing firmly, pull the
cable as far out as it will go; then release. Repeat
three to four times. The cable/exhaust valve should
move freely without binding. If the cable/exhaust
valve does not move freely, the exhaust valve assem-
bly will need to be removed for further inspection.
 NOTE: When measuring the cables, they are to be
routed and as close to their installed position as possi-
ble.
4. While holding the cable housing, lightly pull on one
cable end to remove any slack; then measure the
amount of exposed cable from the cable housing to
the end of the cable.

NOTE: The two cable measurements must be equal
in length or less than 0.5 mm (0.020 in.) difference in
length from each other.