Arctic Power Valve (APV) System

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 horsepower 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.
APV VALVE POSITION
ENGINE MODEL
600 cc Twin
800 cc
600 cc Triple
ENGINE MODEL
500 cc
ONE STAGE RPM RANGES
Acceleration
Deceleration
Down
Up
Down
0 - 6999
7250 and Above 6900 and Below
0 - 6799
6800 and Above 6300 and Below
0 - 6949
6950 and Above 6650 and Below
TWO STAGE RPM RANGES
Acceleration
Deceleration
Down
Middle
Down
0 - 6949
6950 - 7199
6700 and Below
The APV system does not increase engine horsepower,
but it does allow the engine to be designed for maximum top end horsepower without the losses associated
with a “high port” exhaust system.
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 connected 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 recommended 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.
735-476B
AP116A
2. Using a small screwdriver, remove the cable
retaining cover.
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3
„ 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.
AP117A
3. Rotate the servo actuator counterclockwise to
loosen the cable; then pull the cable housings out
of the holder.
0735-516
„ NOTE: Repeat steps 6 and 7 for each cable; then
compare the measurements to the chart.
APV CABLE LENGTH
ENGINE
MODEL
500 cc
600 cc Twin
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.
800 cc
600 cc Triple
MINIMUM
CENTER
MAXIMUM
34.1 mm
(1.34 in.)
32.1 mm
(1.26 in.)
29.6 mm
(1.17 in.)
34.4 mm
(1.35 in.)
35.1 mm
(1.38 in.)
33.1 mm
(1.30 in.)
30.6 mm
(1.20 in.)
35.4 mm
(1.39 in.)
36.1 mm
(1.42 in.)
34.1 mm
(1.34 in.)
31.6 mm
(1.24 in.)
36.4 mm
(1.43 in.)
„ NOTE: The measurements must be equal and
within the specifications from the chart. If the measurements are within specifications, no adjustm 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.
AP118B
„ NOTE: Before proceeding with the cable adjustment, 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.
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.
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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 recommended that only one valve assembly at a time be
removed from the engine.
1. Remove the valve assembly from the engine (see
Section 2).
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)
3
AP121
2. Remove the retaining screw securing the exhaust
valve to the valve stopper.
AP124A
1. Slide the return spring over the end of the
actuating cable.
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.
„ 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.
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AP125
AP120
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).
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).
AP123
AP119
4. Slide the valve assembly into the proper cylinder.
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 recommended 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
„ 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).
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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Assembling/Installing (600 cc)
AP162
3. Remove the retaining pin from the valve stopper.
AP156A
1. Slide the return spring onto the cable end.
„ NOTE: Make sure the small cable end spring
stays in place at the end of the cable.
AP163
4. Slide the valve stopper back on the cable until the
cable end and return spring clear the stopper.
Remove the valve stopper and return spring from
the cable.
2. Place the valve stopper on a clean surface with the
slotted side up; then place the cable in the slot and
pull the cable through the stopper until the cable
end and return spring are in place in the stopper.
Secure with the retaining pin.
AP157
AP164
Cleaning and Inspecting
1. Remove all carbon deposits with solvent and a soft
abrasive such as a Scotch-Brite pad.
„ NOTE: The retaining pin is inserted long end first
from the right side of the valve stopper. Ensure
that the retaining pin washer is in the recess in the
valve stopper.
3. Assemble the exhaust valve and valve guide as
shown.
2. Inspect all parts for nicks, burrs, or other signs of
unusual wear.
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3
AP165
AP153
4. One at a time, slide each of the exhaust valve/
valve guide assemblies through the retaining plate
and onto the pin in the valve stopper.
7. Slide the valve cover onto the studs on the engine.
Secure with four nuts. Tighten securely.
AP119
AP162
„ NOTE: The single center mounting hole on the
retaining plate should be up.
5. Slide the valve assembly into the proper cylinder.
8. Perform steps 6-10 in Cable Adjustment in this
sub-section.
TROUBLESHOOTING
(Carbureted Models)
The APV system has a self-cleaning and self-testing
mode built in. Every time that the engine is started, the
servo will cycle once, and this will wipe-off the carbon
that has accumulated on the exhaust valves. The CDI
unit also monitors the voltages at the servo during this
cycle to assure they are within operational tolerances.
If all voltages are within tolerance, the system is ready
for operation. If the voltages are not within tolerance,
the servo will cycle two more times. If the voltages
remain out of tolerance, the system will not operate.
Problem: Engine loses power; no top end
AP154
6. Secure the valve assembly to the cylinder with
three Allen-head cap screws (coated with blue
Loctite #242). Tighten to 1.1 kg-m (8 ft-lb).
Condition
Remedy
1. Exhaust valves sticking in 1. Remove carbon deposits,
down position
burrs, etc.
2. Cables adjusted too long 2. Inspect—adjust
Problem: Poor acceleration; hesitation
Condition
1. Exhaust valve sticking in
up position
Remedy
1. Remove carbon deposits,
burrs, etc.—inspect/
replace return spring
2. Cables adjusted too short 2. Inspect—adjust
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TROUBLESHOOTING (EFI Models)
Problem: Engine loses power; no top end
The APV system used on EFI models is very similar to
that found on carbureted models. The self-cleaning
and self-testing modes are much alike. The main difference between the two is the higher total electrical
power required by the EFI and APV systems combined. Because of these more demanding power
requirements, the EFI APV system gets power from
the stator lighting coil. The ECU constantly monitors
the power output of the lighting coil, and if the lighting
coil output gets too high or too low, the ECU will activate the “limp-home” mode. The “limp-home” mode
is an ECU operated engine RPM limiter. When activated, the “limp-home” mode will be seen as an immediate loss of engine horsepower.
Condition
1. Exhaust valves sticking in
down position
2. Cables adjusted too long
3. Lighting coil output
voltage out of tolerance
For example, if the headlight and taillight are disabled,
the ECU will sense a high voltage condition and activate the “limp-home” mode. Adding more than 4 amps
of accessories will create a low voltage condition and
activate the “limp-home” mode.
Troubleshooting EFI engines with the APV system
should be done with the Arctic Cat EFI Analyzer (p/n
0644-342). To update your existing EFI Analyzer,
order Kit (p/n 0644-341).
Remedy
1. Remove carbon deposits,
burrs, etc.
2. Inspect—adjust
3. Inspect—replace stator
Problem: Poor acceleration; hesitation
Condition
1. Exhaust valve sticking in
up position
Remedy
1. Remove carbon deposits,
burrs, etc.—inspect/
replace return spring
2. Cables adjusted too short 2. Inspect—adjust
3. Lighting coil output
3. Inspect—replace stator
voltage out of tolerance
„ NOTE: When running an APV equipped EFI
engine on a dynamometer, first connect a Voltage
Regulator (p/n 0603-142, 2-wire) or (p/n 0630-643,
3-wire) between the lighting coil and the ECU.
There must also be a minimum 2.5 amp load
installed in-line between the voltage regulator and
the ECU (a 2.5 amp load is equivalent to one high
beam headlight bulb).
3
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