You will need all the ponies that you can muster, for high altitude Colorado sledding. Everything is above 7000 ft ASL. Check the tunnels beneath the foot wells for buckling from collision damage. Check the tunnels behind the rear plastic molding with the reflector, because they tend to crack there as well. A cracked tunnel requires special braces to stabilize it. Avoid cracked tunnels. People who barely road their sleds, also probably did not know how to maintain them. Check for grease in the bearing beneath the secondary clutch. No grease means they were an amateur and the bearing could already be screwed up. You have to have a lot of experience to be able to replace that one. Most other bearings need replacing by 3000 miles. Check the left front engine crankcase to frame bolt. That bolt tends to blow every 500 to 1000 miles on the 800's. A torn one means the crankcase has been twisting and causing excessive wear on the crankshaft bearings. Avoid buying used sleds with over 1500 miles, unless you know your stuff about maintenance.