Is it 2 or 4 stroke? If its a 4 stroke then check these:
Chain case seal leaks(common leak on the jackshaft input side of case)
Muffler rubber mushrooms pad things(if bad the mounts can wear into the muffler)
JackShaft bearing on clutch side is known to fail
Look over the rear skid good, they used the same hardware on the heavy sleds as they did on the lighter sleds.