Snowmobile Arctic Cat (2004 year). Manual - part 39
3-19
3
738-232A
The Arctic Power Valve (APV) System adjusts the size
of the exhaust ports to produce maximum horsepower
on the top end while providing excellent low end
power and increased touring fuel economy.
THEORY
Two-cycle engines and their exhaust systems are
designed to produce maximum horsepower in a given
RPM range. This RPM range will change according to
how high (or low) the exhaust port is in relation to the
cylinder. Engines designed for racing have a “high
port” exhaust system and will produce more horse-
power at higher RPM but only with the loss of low end
power and overall fuel economy. “Low port” engines
will produce maximum horsepower in the low RPM
ranges and provide good mid-range fuel economy, but
they sacrifice top end performance.
The APV system does not increase engine horsepower,
but it does allow the engine to be designed for maxi-
mum top end horsepower without the losses associated
with a “high port” exhaust system.
735-476B
COMPONENTS
The main components of the APV system are the
exhaust valves, return springs, actuating cables, and
the servomotor (servo).
The exhaust valves are connected to the actuating
cables and, along with the return springs, are contained
inside the APV housing on the exhaust side of each
cylinder. The other end of the actuating cable is con-
nected to the servo. There is also a vent hose on each
APV housing to relieve the pressure of “blowby”
gases that may escape from the cylinder.
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
CDI/ECU will send a signal to the servo which will
cycle and pull the exhaust valves into the up or “high
port” position. The RPM at which the valves open is
different with each model.
MAINTENANCE
The APV system requires only periodic cleaning and
cable adjustment. The cables should be checked every
1000-2000 miles and adjusted as necessary. To ensure
maximum performance and minimize maintenance
requirements, Arctic Cat recommends using Arctic Cat
Synthetic APV 2-Cycle Oil. Using oils other than the
recommended oil may increase the frequency of
required cleaning due to increased buildup of carbon
deposits.
CABLE ADJUSTMENT
(Standard Models)
Proper cable adjustment is critical to the operation of
the APV system. While it is recommended that the
cable adjustment be inspected every 1000-2000 miles,
the cable should not need adjustment often. To check
the cable adjustment, use the following procedure.
1. Remove the two bolts securing the servo cover.
AP116A
2. Using a small screwdriver, remove the cable
retaining cover.
APV CABLE LENGTH (“Laydown”)
ENGINE MODEL
CENTER
± 1 mm (0.039 in.)
500 cc
34.5 mm
(1.35 in.)
600 cc
34.5 mm
(1.35 in.)
700 cc
34.5 mm
(1.35 in.)