Funny you should ask. I put a Dakota clutch on my F7 and was warned to remove the thin shim on the driven or get belt slip (I had only three, two thicker than the third. I removerd the thin one) That was good advice; my sled absolutely rips now. What's more, I just get back from Paradise and get an email from Black Magic about clutching. Here's the info:
Belt Length-----Always Important
While riding and continuing our testing on the new F7, we are continuously going back to our original setups to verify our gains and/or losses in performance. A couple of weeks ago we went back to our "baseline", if you will, only to find that we had lost a ton of performance. The RPM levels were slightly off, but the actual performance was way down. Our times in 1000 feet had dropped by 2 to 3 tenths from our original testing with the stock baseline.
Where had all of this performance gone? With all the talk of engine seizures etc. with the F7, we presumed we had inadvertently hurt the cylinder or pistons on the vehicle. We immediately checked the level of compression, verified the condition of the pistons and found nothing wrong.
We then went to the clutching system to see if we had any real problems. While the belt appeared to be a bit loose, it did not look to be the source of our problem. The drive and driven clutches were removed and thoroughly checked out, with nothing appearing to be out of order.
The sled was reassembled and tested again. Same results, slower than a toad and just not right. So just to make sure everything was correct, we took an .030 shim out of the driven clutch to make the belt work like a belt that was shorter. We went out for a ride and presto, instant performance like it was before. The rate of acceleration was back, the level of RPM was proper, and all in all, our little rocket ship was now working properly again.
So the moral of the story, never overlook the simple things. Performance on a snowmobile comes with making sure everything is working as designed. There is no such thing as a magic wand to make them fast, only TLC and the constant attempt to produce perfection.