I remember reading an article about the RM250T-which I had just bought new-and the engine mounting bolts were of a smaller diameter to the case holes.This,they said,was the cause of some broken engine mounts.As the other guys have stated,drilling out and going larger or shimming out -both will work.I just rebuilt a 125D with ovalled front engine mounts and worn cases from the movement here-I just shimmed it out and used nyloc nuts with loctite and all good for about 2 years now.