I have a KT17QS series II engine on my 317 that I replaced on 9/16/04 and had it in storage about 5 years (I turned it on every so often). I have an hour meter on my tractor. I measured the compression three years ago at 90psi and about 237 hours of operation. The engine seems to be running well right now except I think I smell the exhaust a bit more. I did have a problem recently where it was running hot for a couple mowings (3 hours) and after thinking it was running lean and needed to service the carb, I opted to replace the carb and that resolved the problem. However, recent compression tests (after 365 hours of operation on the engine) indicate one cylinder is at 80psi and the other 75psi which is low according to what I have read. It seems like this is not many hours on the engine. Do I have need to be concerned? What could cause the lowered compression? I did just add Sea Foam to the crankcase but have no hours yet on the tractor with it.