Hey guys,
I flew the Thunderbolt again this past weekend and lost a muffler. In talking to a few of the guys in the office, this is pretty common on the Evo engines. Seems like there is some type of expansion/contraction issue between the engine and muffler that is not entireably compatible.

I had this issue on the Evo 80 and was not aware of it on the smaller engine.

Ths fix I have is to use a 5mm x40mm bolt and drill the head of the bolt for a safety wire hole. The bolt head lives on the outside of the muffler. Once installed, you safety wire the bolts with some .025 stainless safety wire and they never come loose again. I will post pictures within the week for reference. Just wanted you guys to know of the issue I had come up with and what the fix was. This fix has been flying on my Robart P-47 /Evo 80 combo for over 2 years now.