I just picked up an 06 sportsman 450 about two weeks ago. It seems to be in really good shape except for two things that I have noticed so far. The smaller issue is that switching through the gears is pretty rough without help from the display. When you move the slector to where reverse is, it sometimes doesn't engage. You have to ease the lever back and forth slowly to find the gear. I dont know if thats normal for this ATV but if not then i would like to know how to make it better. The thing that has got me concerned is that after driving it for a short time, when you do anywhere from a half to full turn it starts to squeel like a slipping belt on a car would sound like. It continues to squeel after you straighten back out for a bit until you either accelarate quick or slow to almost a stop and then accelarate. I have done a tune up and changed all the fluids on it, also did an external inspection but cant seem to figure out what is causing the problem. Any help would be greatly appreciated.

 

Pull the front wheels,turn the rotors to see if there is any warping or grinding from the caliper or pads.Inspect the cv joint for any tears in the boot or for excessive play that may be making the noise. Plus the squeal could actually be from a worn or glazed belt if you can't find anything wrong with the brakes or cv.As far as hard shifting,may be time to remove the small cover on the gear case and inspect the small gears and spring. These can get moisture and rust making shifting hard. Items are behind the cover(part#3) on the thumbnail pic.Plus here's a few pics that someone posted on his 700 from Polaris Atv Forum. Gear case is similar to yours.Hard to Shift 700 Sportsman 2004 - Polaris ATV Forum