Snowmobile Arctic Cat (2002 year). Instruction - part 50

 

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Snowmobile Arctic Cat (2002 year). Instruction - part 50

 

 

3-23

3

Arctic Power Valve

(APV) System

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 Oil. Using oils other than the recom-

mended oil may increase the frequency of required

cleaning due to increased buildup of carbon deposits.

CABLE ADJUSTMENT

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 VALVE POSITION

 ENGINE MODEL 

ONE STAGE RPM RANGES

Acceleration

Deceleration

Down

Up

Down

600 cc Twin

0 - 6999

7250 and Above

6900 and Below

800 cc

0 - 6799

6800 and Above

6300 and Below

600 cc Triple

0 - 6949

6950 and Above

6650 and Below

ENGINE MODEL

TWO STAGE RPM RANGES

Acceleration

Deceleration

Down

Middle

Down

500 cc

0 - 6949

6950 - 7199

6700 and Below

3-24

AP117A

3. Rotate the servo actuator counterclockwise to

loosen the cable; then pull the cable housings out

of the holder.

AP118A

4. Pull the cable up and out of the cable housing

holder; then slide each cable drum to the left and

out of the servo actuator.

AP118B

„

NOTE: Before proceeding with the cable adjust-

ment, ensure that the exhaust valves are free to
move. 

5. 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 assembly will need to be removed for further

inspection.

„

NOTE: When measuring the cables, keep them

as close to their installed position as possible.

6. While holding the cable housing, lightly pull on

one cable end to remove any slack.

7. Measure the amount of exposed cable from the

cable housing to the end of the cable.

0735-516

„

NOTE: Repeat steps 6 and 7 for each cable; then

compare the measurements to the chart.

„

NOTE: The measurements must be equal and

within the specifications from the chart. If the mea-
surements are within specifications, no adjust-
m e n t   i s   n e c e s s a r y.   I f   t h e y   a r e   n o t   w i t h i n
specifications, proceed to step 8.

8. Loosen the jam nut on the cable to be adjusted;

then using the adjusting nuts, lengthen or shorten

the housing as needed.

0735-837

9. Once the proper length has been attained, hold the

adjusting nut in place and tighten the jam nut

securely. 

10. Install the actuating cables into the servo.

APV CABLE LENGTH

ENGINE 

MODEL

MINIMUM

CENTER

MAXIMUM

500 cc

34.1 mm 

(1.34 in.)

35.1 mm 

(1.38 in.)

36.1 mm 

(1.42 in.)

600 cc Twin

32.1 mm 

(1.26 in.)

33.1 mm 

(1.30 in.)

34.1 mm 

(1.34 in.)

800 cc

29.6 mm 

(1.17 in.)

30.6 mm 

(1.20 in.)

31.6 mm 

(1.24 in.)

600 cc Triple

34.4 mm 

(1.35 in.)

35.4 mm 

(1.39 in.)

36.4 mm 

(1.43 in.)

3-25

3

SERVICING

There are two styles of power valves in use in the 2002

Arctic Cat engines. The “flat style” valve is on the 500

cc and 800 cc engines, and the “round style” valve is

on all 600 cc engines.

Removing/Disassembling

(500/800 cc)

„

NOTE: To avoid a parts mix-up, it is recom-

mended that only one valve assembly at a time be
removed from the engine.

1. Remove the valve assembly from the engine (see

Section 2).

AP121

2. Remove the retaining screw securing the exhaust

valve to the valve stopper.

AP123

3. Hold the valve stopper securely and pull the cable

back and up until it clears the top of the stopper;

then slowly release the cable and remove it from

the valve stopper.

AP125

Cleaning and Inspecting

1. Remove all carbon deposits with solvent and a soft

abrasive such as a Scotch-Brite pad.

2. Inspect all parts for nicks, burrs, or other signs of

unusual wear.

Assembling/Installing

(500/800 cc)

AP124A

1. Slide the return spring over the end of the

actuating cable.

„

NOTE: Make sure that the small cable end spring

stays in place at the end of the cable.

2. Place the valve stopper on the cable and slide it

down until the cable end is inside the stopper.

3-26

AP125

3. Slide the exhaust valve through the retaining plate

and insert it into the valve stopper. Secure with the

retaining screw. Tighten to 0.6 kg-m (4 ft-lb).

AP123

4. Slide the valve assembly into the proper cylinder.

AP121

„

NOTE: The flat side of the retaining plate must

be down.

5. Secure the valve assembly to the cylinder with two

Allen-head cap screws (coated with blue Loctite

#242). Tighten to 0.9-1.3 kg-m (6.5-9.5 ft-lb).

AP120

6. Slide the valve cover onto the studs on the engine.

Secure with four nuts. Tighten to 0.9-1.3 kg-m

(6.5-9.5 ft-lb).

AP119

7. Perform steps 6-10 in Cable Adjustment in this

sub-section.

Removing/Disassembling (600 cc)

„

NOTE: To avoid a parts mix-up, it is recom-

mended that only one valve assembly at a time be
removed from the engine.

1. Remove the valve assembly from the engine (see

Section 2).

AP154

2. Slide the exhaust valve/valve guide assembly off

the retaining pin and free of the valve stopper.

Repeat with the second exhaust valve/valve guide

assembly.

 

 

 

 

 

 

 

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