I have a 1978 Arctic Cat Pantera 5000 with the fan cooled engine. It has a Comet 94c duster clutch on it. I have to rev the sled up a little ways to get the clutch to engage. It eats belts if I nail it to much at lower speeds. And when I run it at WOT it doesnt seem to go that fast my brother with a 1985 Pantera 440 said he was only going about 1/2 throttle and going about the same speed as me. I see they sell spacers for belt width. I was wondering if being too wide would cause these problems. But I have also heard the duster is to big for a 500.