The past two days I've been out flying my raptor 30, the muffer has unscrewed itself. I've tightened good, and retorqued it when the engine/muffler was warm. But still it comes loose. Almost lost my beloved this evening, when it came loose in flight. Fortunatelty the engine did not quit on me, so I managed to fly it back and land it safely. (Need to learn autos)

Do any of you have good tip on how to fasten the muffler so it stays in place? Another thing, there is a aluminium washer between the engine and muffler. (The muffler is a Zimmerman muffer.) Is the alu washer needed?? I think that bugger is the reason... Never seen a alu washer between eng/muffler before, and I've been flying airplanes for many years...