The GMS and Tower mufflers are exactly the same and have the same "rotating" problem.

However this is easily cured.

Everyone ( including myself ) assumes that the lock nut at the back of the muffler is what is supposed to hold the whole assembly together.

We tighten it down, and then are surprised to find the muffler loosening or rotating in flight.

I've tried JB Weld on the whole thing and merely end up making a mess, as the JB weld will dissolve with the heat and glow fuel...


Instead of all of this, leave the locknut off initially.

The long screw threads into the back end exhaust part of the muffler. This is what you need to get tight and assure that it will not turn.

Remove the cardboard washer from the long screw. Insert the screw and assemble the muffler as usual. Put in Locktite at the screw or receptacle.

Tighten it down carefully and as hard as you can WITHOUT stripping or hurting the screw head.

This will pull the back end towards the front.

Now grab a heat gun or torch and heat up the junctions of the cylinder.

You'll find that the scew is loose again. Tighten it down as much as possible.

Repeat the heat cycle and tightening.

Finally install and tighten the rear lock nut... preferably install a second one against it to prevent them both from turning in flight.