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2 OS fs.91 mufflers with worn threads-Problem & fix?

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Old 07-26-2011, 05:49 AM
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xcz5785
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Default 2 OS fs.91 mufflers with worn threads-Problem & fix?

I have two OS fs91's one is old one is II. the old one has gone through two mufflers and now the II HAS JUST DESTROYED ONE. I am sick of buying muffles and now I think they are discontinued. They were tight and the prop is balanced. What do I do now? Is there a M11x.75 helicoil? I've searched and found just a tap. HELP!
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Old 07-26-2011, 05:52 AM
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Default RE: 2 OS fs.91 mufflers with worn threads-Problem & fix?

We don't know of a helicoil for the O.S. exhaust threads.

Usually, the threads in the cylinder head break because the muffler is not supported and will move about as the engine moves about. Flexible airframes are as much a cause as anything else. The muffler should be supported at the airframe, and the structure should be firm enough that the engine will not move about as it runs.
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