Arctic Cat has provided us with a step-by-step procedure on cleaning the APV exhaust valves. These valves can become sticky and carbon up after many miles and hours of operation. Factors like type of oil used, operation conditions and driving habits can affect how often the valves need to be serviced.
Cleaning the carbon deposits from the exhaust valves ensures consistent performance and also improves fuel economy. As the valve is pulled up and down in the cylinder, it varies the height of the exhaust port and the port timing itself. Consistent positioning is achieved via a servo motor and cable. Keeping the valves clean ensures smooth movement and quick positioning.
Step 1: (The entire process is easier with the exhaust pipe removed.) Begin by removing the (opaque) plastic cover over the servo motor (where the cables from the valves run to).
Step 2: Itâ€™s critical to mark (index) which side of the servo pulley the cables attach to. Use a felt tip marker and youâ€™ll eliminate guesswork during reassembly. Remove the black steel cable / housing retaining clip that holds the cables / housings in the servo retainer.
Step 3: Either rotate the servo slightly or pull the cable housing down to create slack in the cable. Slide the rear (closest to the fuel tank) cable end out of the motor, followed by the front cable. Then pull the cable / housing out from between the cylinders (Itâ€™s easiest to first remove the plastic retaining clip that holds both cables together).
Step 4: Working with one valve at a time, remove the two hex bolts that attach the valve assembly to the cylinder. Gently pull the valve out of the port, taking special note of how the guillotine-shaped valve was originally installed (on most engines, the long end of the valve faces up).
Step 5: Using a spray cleaner (brake cleaner, carb cleaner, oven cleaner) spray the guillotine valve, let it sit for a few moments, then use a wire brush to scrub away the rough carbon deposits on all sides of the valve (carefully select a brush and use care so you do not damage the valve).
Step 6: Reinstall the clean valve into the cylinder (we like to lightly lube it with injection oil beforehand), and repeat steps 4 & 5 with the other cylinder (s). When all valves have been cleaned and reinstalled, reroute the actuating cables to the servo. Perform the APV cable length measurement/adjustment outlined in your operatorâ€™s manual. Reinstall the cables into the servo (on the side you marked), reattach the plastic cable housing retaining clip, as well as the steel cable / housing retaining clip. Reattach the plastic servo cover and exhaust system.