cases are ported on both sides just below the cylinder. It looks like it was machined out to open up airflow and oiling. I would have to show you on a case picture to make it easier to understand. The gears on the crank were replaced. If the quad doesnt sell im just going to strip the motor and put the bottom end and head on a 525 for next year, put it back close to stock then clearance price it. Just trying to avoid it and make a quick couple thousand for other projects.