So your Polaris has good horsepower, the chassis works the way you want it to, you have tuned the clutches to perfection and the sled works as well as it can. Or does it? Power is being robbed in the clutch system and too often it is assumed that if the clutch moves and propels the sled that it is working to the maximum potential. There is more power in your clutch and we will explain how to get it out. The following performance tips will make your Polaris faster, improve belt life and in some cases even enhance fuel economy. This is not new information, most of which has been practiced by the most successful snowmobile racers for many years.
The first issue to address is drive clutch belt side clearance. Variance in belt side clearance can even be seen in identical new sleds where one is faster than another. The weight arms that actually control the moveable sheave have a "range of efficiency". In this operating range is where the belt will have the necessary side pressure to prevent or reduce slippage and the shift out will be aggressive up to maximum mechanical ratio. If there is excessive belt clearance it can cause poor off the line performance, hesitation, bogging, belt burning as well as reduced acceleration and less top speed. Many times a low speed bog will be blamed on the carburetors simply because it has the same symptoms but in fact it is due to excessive belt clearance.
Belt side clearance on the drive clutch is measured with a new or very good belt in place, push the belt to one side of the clutch shaft, then simply slide a feeler gauge between the side of the belt and the sheave of the clutch. Ideal clearance should be .010" to a maximum of .020". This would be with only slight friction on the feeler gage when testing clearance. If there is more than .020" clearance than one or all of the above symptoms may or may not be present but you are losing performance. Adjusting the clearance is done by removing the spider and adding or subtracting shims as needed. A variety of thickness shims are available from a Polaris dealer. SLP has all the special tools available clutch service and for removing the spider properly.
The second issue basically has to do with cleanliness. All belts when you buy them new will have a trace of mold release from the manufacturing process. This mold release will transfer to the clutch faces and absorb into the pores of the aluminum. This material present will increase the possibility of slippage and of course, power reduction to the ground. Other contaminants such as oil, grease and gasoline are also an issue. Build up of rubber on the clutches can also reduce performance. The first caution about cleaning is to never use any solvent based cleaners. These would include petroleum, alcohol, cleaning solvent and miscellaneous chemical based products such as carb cleaner, brake cleaner, electric contact cleaner, parts washing solvent and so on. On the most part, residue from these products absorb into the pours of the aluminum or simply wash contaminants into the pours to come out latter and become permanently attached to the belt causing slippage. I have heard of hundreds of cleaning methods over the years but only one method that is really effective.
Use a piece of scotch brite pad or steel wool to scuff off any heavy rubber buildup on the clutch faces. For heavy buildup you can use 180 grit sand paper with caution not to over sand and create low spots. Then wash the clutch faces with hot soapy water (hotter the better) since the heat and soap will tend to draw contamination from the aluminum. Finish by wiping dry or air blow dry. The belt must be cleaned also using a medium to soft bristle brush and the hot soapy water to remove contaminants. Dry the belt completely before installing. Be sure not to overlook clutch compartment cleanliness as well. If the compartment is coated with belt dust, oil, fuel weeds and whatever you can just guess where it will eventually end up.
The next step is to reinstall the clutch and perform all needed adjustments. Clutch offset and center to center distance is very important for proper clutch and belt function. If the offset is off it will cause more pressure to one side of the belt than another which results in excess temperature, wear, slippage and performance loss. If belt free play is excessive it will cause the belt to pull up into a higher ratio at engagement causing sluggish performance off the line as well as excess temperature, wear, slippage and performance loss. One rule that is beneficial for belt free play is to run the belt as tight as possible without creeping at an idle. This insures that the belt will stay in low ratio for a spunky hole shot. Most sleds can benefit from a torque arm (and push arm on some models) to hold the engine and alignment in place. Performance as well as belt life is improved. SLP has torque arm products for most Polaris models.
Clutch balance is another issue that is often overlooked. The smoother it runs the smoother it operates. An out of balance clutch will continually hammer away at main shaft bushings in turn reducing smooth and efficient movement. This hammering creates accelerated wear on main shaft, roller and weight bushings as well. Balancing can also prevent damage to the crankshaft since this hammering will eventually damage the case and/or bearings. Just a note, the majority of the time you can not detect this vibration created from an out of balance clutch until it is too late.
The spring quality and condition is something to be aware of to maintain the best performance. Springs are a wear item that can loose tension or response over a period of time during operation. A rule for spring replacement should be once per year or at least every 2000 miles. Removing the springs from the clutches during storage months so it is not compressed will also add life to it. Finally, choose good quality springs for best performance. The material that the spring is made of will certainly have an effect on how "snappy" the performance is. SLP offers a selection of high quality springs that will have better performance and life expectancy than the springs that you can typically buy for your sled.
It seems like I have given you a long list of work to do. How well do you want to perform? How much of the power do you want to transfer to the ground. Once you have completed this clutch "super tune", keeping them in good condition will come easier. You will enjoy the added performance and the savings for parts and fuel.
