Just because nothing seems wrong doesn't mean nothing is wrong. Shortly after I got my first sled, a 96 vmax 600, I was driving it and all the sudden I thought I blew it up. Nope, engine was fine. Figured out it was the clutch. When I rebuilt the clutch you couldn't tell anything was wrong with it. But put it back on after the rebuild and it works perfect now. Had a similar, but not the same issue on my srx and it was the secondary. Have to remember when it is pushing on the belt it only has resistance on half of the clutch. The other half is trying to go in further still and can cause it to bind just enough. I also had a problem with my viper this year. When I would go full throttle it would bog and never recover unless I would let off. Yet sometimes it worked fine for a minute. All I had was a new secondary spring to try. Put it in and it was good as new. Couldn't believe just the spring change did it. Hope this helps.