Anyone else having problems with the newly desinged muffler on the US Engines 41CC?

After flying 3 flights on a NEW engine the muffler was loose. Here is what I found:
1. The aluminum muffler block is threaded.
2. The gasket was totally destroyed; only the metal remained.
3. I removed the old gasket and it appears the bolts do not draw the muffler up snug against the exhaust port on the cylinder.

My fix for now is to remove the threads from the muffler and get a good metal to metal match. Then install a new gasket and try again.

Any suggestions?

Garry

These engines have had muffler problems for years. They were designed for a 4 bolt tin can muffler. Look at the exhaust flange, it is a very thin lip of aluminum so the muffler needs to be supported all around. Look at the flange on other engines and you will see a larger and wider flange mating area that supports aftermarket mufflers and header pipes better. I thought when US Engines finally got rid of that tin can and started selling their engines with a real muffler that you could use, they were making real strides to sell a RTF product. The muffler that now comes with them is very restrictive( although fairly quiet) and does have a habbit of coming loose. Have had better luck with a B&B style muffler, and we started drilling the socket head screws and safety wire them just as the full scale aircraft do. Also, use the red locktite on the threads.

Lenny,

I completely agree with safety wire. I could not stop my muffler from coming loose on my US41 until I wired the bolts.

I have also been told to use the red Lock-Tite. Have you had any problems backing out bolts that had been set with the red stuff?

Bedford

The problem sometimes is the gasket. If you locktite the bolts and run the engine a few times, the gasket shrinks, and even though the bolts have not backed out, you end up with a loose muffler. Once there is a few thousandths of play, the gasket falls apary rapidly and you have even more play, and the bolts are where you put them, and have not backed out. I do NOT use a gaslet anymore and use a thin layer of high temp RTV and have had much better results.