I flew this morning and everything went fine. After I landed I took the headset off as I was taxiing back between the hangers. The engine started making the most awful hammering sound. It sounded like the connecting rods were about to come through the side of the crankcase or the exhaust pipe was falling off! I got to my hanger and shut down. Then I realized I could still hear the hammering. I looked around and saw one of my neighbors running the two stroke engine on his trike. Made me wonder how you tell one is broke!