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Engine basics => Engine set up tips => Topic started by: Dennis Toth on April 24, 2014, 07:18:50 AM

Title: OS FP25 muffler tail cone nut - what does it do?
Post by: Dennis Toth on April 24, 2014, 07:18:50 AM

Guys,
I was working with my K&B 40 fitting the OS FP25 muffler and wanted to reposition the angle of the exhaust so I started to loosen the rear nut and found it just kept turning without releasing the tail cone. It wouldn't come out just spin. I loosened the front bolt and it released the tail cone and I was able to repostion it where I wanted. I retightened the nose bolt the whole muffler is tight but the tail nut still spins, does anyone know what the tail cone nut does in these mufflers?

Best,     DennisT

Title: Re: OS FP25 muffler tail cone nut - what does it do?
Post by: Andrew Hathaway on April 24, 2014, 08:46:22 AM

It's a jam nut to lock the assembly together.  The nut should snug up tight against the cone, if it doesn't it sounds like the bolt or the nut might be stripped. 

Title: Re: OS FP25 muffler tail cone nut - what does it do?
Post by: Paul Smith on April 24, 2014, 09:57:50 AM

Correctomundo.

The long bolt is threaded into the tail cone and the back nut is somewhat redundant.  But the combination does a good job of holding the thing together. 

Title: Re: OS FP25 muffler tail cone nut - what does it do?
Post by: Bill Heher on May 31, 2014, 07:27:05 PM

without the nut on the end the screw can vibrate loose. it will eventually unscrew from the outlet end, finally the end of the muffler falls off and your plane will get real loud, and if using muffler pressure it will lean out and start screaming around at max rpm until you get behind it and crash - not that it ever happened to me........