Probably start by doing the same thing this guy suggusted to the other guy:
"I am not an expert and I am sure others here may give you the same or better advice, but it could be a multitude of things. I'd check with the simpler things like the belt, track tension, give it an all around tune up and go from there. As far as suspension...Shocks?? Just start loosening the bolts on the chain case and all the oil will run out. Just watch to where it might run out, should come out hole in pan for muffler. Hope that helps a little. Good luck!"
Try searching the forum for performance or speed or clutching or jetting or Polaris 440. You get my drift. Most of this stuff has been talked about a lot. Then if you have questions ask them and we will be glad to help out.
A forum community dedicated to snowmobile owners and enthusiasts. Come join the discussion about performance, racing, troubleshooting, trails, maintenance, riding tips, modifications, classifieds, gear, and more!