The triple 600 motor was a good engine if you took care of it. Make sure to look at the airbox boots to ensure there aren't any cracks in them. They also had some problems with the right front motor mount breaking but they had an update for that.The exhaust pipes sometimes had a tendency to pop out of the exhaust manifold on the engine but if you put double springs on the pipes this solved the issue. Also some guys would run a bead of high temp silicone along the exhaust springs to eliminate vibration and spring breakage. Other than that check all the normal things like idler wheel bearings, chaincase bearings, clutchs, track. You might want to pull the pipes and look in the cylinders to see how the pistons are wearing.
Let me know if there is anything else I can help you with
Jeff
Gold CatMaster Mechanic
www.FunOutfitters.com
Free Technical Support Line: (866) 531-0123