I don't have the model number but it's posted on here somewhere. I rebuilt this motor in June of last year and the damn thing broke a ring a week ago. Any ideas on what would cause the ring to just let go? We went through the carbs, took the VRO off, ran BRP XD 30 oil, and 93 octane gas ( had the heads shaved). Alll three spark plugs looked the same on the port side cylinders. It was getting oil/gas and there was no sign of the motor overheating.