I highly doubt putting in only new pistons will magically cure bad compression. I suspect cylinders would need to be bored ($$$) and then get wiseco/oem pistons ($$$). Might be better off buying a whole motor (400, 440 or 500 will drop right in without modifications) for less than $250. But then again, it's an 89 400, you don't want to dump a ton of money in it. A mint one would sell for $500-$600 tops in the late fall, or 200-300 bucks now. YOU are the one that has to decide if it's worth it or not.
A wiseco kit won't give you any more power than stock-from-the-factory pistons. But obviously it will give you a running motor seeing as yours currently has bad compression.
Prob just need rings. But if your pistons are out of spec due to high mileage, then replacing them is a good idea. Dont bother with oem, too pricey, and stay away from wiseco unless you have your cylinders redone to fit them exactly.
Expensive pistons wont give you any extra hp, but fixing the comp issue will help.
How many miles does that motor have?? One of the guys in our group has around 9000 on his and it runs like a top, also I have been told to recheck the compression when the engine is hot, see if its any better after running before you go tearing it all apart.
A forum community dedicated to snowmobile owners and enthusiasts. Come join the discussion about performance, racing, troubleshooting, trails, maintenance, riding tips, modifications, classifieds, gear, and more!