I just returned from the airport after a close inspection of the engine with two A&P's who hangar close by me. I removed the top cover to inspect the inside of the case and removed the spark plugs so we could freely turn the crank and cam. Absolutely nothing we could see would indicated a sudden stoppage of the cam causing the failure. Everything turned smooth and freely. I also had a discussion with William this morning and he may have hit the nail on the head. For some reason, not yet determined the crank gear was causing wear on 180° of the cam gear teeth. Beginning exactly with the tooth with the timing mark stamped on it, you can see a wear pattern starting to develop. With each progressive tooth for 180° to the point of failure, the teeth wear became more pronounced until the final teeth were like a knife edge. This led to the breaking of the tooth and grinding away the following few teeth. So, what does this tell us? Was the gear run out bad? The remaining 180° of teeth exhibited little to no wear. There is no doubt that this wear was happening from the initial startup from the rebuild and took 4.5 hours to reach a point of failure.
Mark Jones (N886MJ) Stevens Point, WI Web page: www.flykr2s.com e-mail: flyk...@charter.net
