hello, I have a friend who has a liquid cooled 400 (sport I believe) polaris with a expensive reoccurring problem. I have ordered two replacement cylinders for him in a years time because the cylinder has been lifted off the block on just the two rear studs, busting the front of the cylinder (obviously). Can anyone please tell me if this is a common problem or possibly what causes it and how to remedy it? Thank you

 

After two top ends,no this is not a common problem.. I think I'd start checking into the lower part of the engine and work my way up. Crank out of balance,lower rod bearing,crank bearings,possible a combination of all of these.Sometimes hard to get by on just top ends on the old 400 engine. Just too many components in this engine that have to be working right.