I have an o.s. 61 FX with a slimline pitts muffler that was on an ill-fated Cap. After crashing the Cap, both of my stacks on the pitts muffler were badly bent and cracked at the base. I repositioned the stacks and used JB Weld to glue the stacks back in place. Well, the muffler went on another .61, and is in my Shoestring right now, and I thought everything was great. However, after taking off my cowl and inspecting the engine after about 20 flights, one of the stacks appears to be coming off, and the JB Weld is virtually being eaten up by the 15% nitro. Is this possible? I can only attribute the fuel getting to the stacks in large quantities from a few tank overfills, where excess fuel comes out of the muffler when I am all fueled up.
If I get the whole mess cleaned up, is there another way for me to attach the stacks successfully? Please give me any input or advice on the situation. My first impulse would be to just buy another muffler, but I cant seem to find a hobby shop ( I have called eight, and I live in a LARGE metropolitan city) that has one in stock. By the way, I would order, but I need to fly by this weekend because we are having our yearly fly in.
Thanks, Mike

The JB Weld is a nightmare on 4 stroke mufflers. The Slimline is fabricated from thin wall tube that is joined with an aluminum brazing alloy. In orde for successful repair by rebrazing the surface must be very clean. The JB when heated gets right into the aluminum and must be completely removed . There are very few adhesives that will give a suitable bond in this application.

You might consider contacting Slimline and explaining the situation. It can't hurt.
If they can't help send me a PM and I'll see what I can do to help.