Just thought I'd post a couple pics of the main bearing I recently turned for my caterpillars pony motor. The blank was cast out of aluminum pistons, I read that they were a suitable alloy for this application. Guess I'll see how it works, new bearings were over $100 apiece from cat so I thought it'd be worth a try. I turned down the crank and polished it with three grades of emery then made the bearing .005 over that as this little motor doesn't have pressure lubrication .