Clutch Inspection for the 120's
To verify a stock 120 clutch without taking it off the snowmobile, check at what rpm it starts to "tick the shoes against the drum". A tachometer is needed to clip on the spark plug wire and a ground. The person would have to turn the throttle very slowly to get an accurate reading. We took 10 clutches at random to verify at what rpm the shoes start to tick against the drum, They "tick" from 2,400 rpm up to 2,700 rpm. Higher than 2,700 rpm, the clutch tries to move the snowmobile forward. The SS1034ILW clutch will engage the drum prior to 2,700; If It doesn't then we would conclude the spring or the shoes have been altered for a higher engagement. Switching shoes to the lighter 46 gram shoe would bring up the engagement considerably. The shoes in the 120 are referred to as our "wedge shoe" and will completely fill in the void of the backing plate created when we stamp and form the tabs on the drive plate. If you see daylight around the shoe, then it has the the lighter shoe in the clutch that we use in the Kitty Cat.
Remove the clutch from the snowmobile and take the drum off the shoe assembly by removing the outside snap ring. If you see that the inside portion of the drum that makes contact to the shoes is bare steel with no black oxide remaining then most likely the drum has been "trued up" which Max-Torque does but not to stock clutches. The stock clutches are black oxide and have not been trued. A trued up clutch drum will measure 3.998 to 4.000 on the ID with a dial caliper. The trued up drum can be purchased from Max- Toque by a distributor or dealer but it is not a stock clutch drum.
After you take the shoe assembly apart, verify the weight of the shoes. We spec out that the "SS" (six shoe) weigh 62 grams +/- 1 gram. Anything less then 60.5 grams would call for closer Inspection. Yes, there will be some wear to the shoe but the drum would get fairly grooved before the shoe would show any wear.
The last thing to verify Is the spring length which we spec out at 9.050 to 9.150 and the wire diameter should be .058 +/- .001. This measurement is made on the outside of the two loops by placing the spring inside a 12" caliper. The spring we provide is painted green but older clutches may have a red spring in them. Everything is the same for a red or green spring just that they are different manufacturers. Every spring is inspected by us prior to the assembly to make sure it fits within those guide lines. Short springs are difficult to assemble so they don't get out of the facility with a short spring.
The single digit number stamped on the back of the drive plate just indicates the year we stamped the drive plate.
Max-Torque can inspect questionable clutches to verify if they have been altered. The only charge would be for the UPS back to the club. We would suggest that the tech people have several spare clutches on hand to swap out for the questionable clutch. The same day we get a clutch it would be sent back with a note by us saying it was stock and within our specs or it was altered.
The Arctic Cat clutch will fit the Polaris 120 but the Polaris will not fit the Arctic Cat 120 because Polaris a #40 chain sprocket (.285 wide) and Arctic Cat uses a #41 chain sprocket which is .227 wide. There are other slight differences between the two clutches but these are not going to make it perform any better. Polaris uses a one piece hub and sleeve while Arctic Cat is a two piece hub and sleeve that has been press fitted together. The internal key used in the Polaris hub is twice as long as the Arctic Cat clutch. Polaris uses a lube clutch that has a hole drilled into the sleeve to allow grease into the bushing of the clutch.
James F Donovan
Vice President and Owner