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...

No! you don't need the washer. I have been running mine for two years with out a gasket and have never had a problem. I would try red loctite on your muffler bolts (make sure you let it dry overnight) that sould do the trick.

You also need to clean the bolt threads and the threaded hole in engine with rubbing alcohol or the thread locker will not work as well. Tim.

Thanks for the answers, I'll try to remove the washer and locktite the bolts.

Unfortunately it's raining today here in nothern Norway, so I need to wait for better weather to try it out.

Well it's been a while since I've tried this out and here is what I've done: Removed the washer (big improvements), bolted the muffler in place and then used nuts on the bolts to clamp the muffler to the engine. Locktited the bolts to the enging and used CA between the bolt and nut! Works like a dream No more loose muffler!!