Uhh, hang on a minute. If the mixture is set right, the exhaust gas temp ought to be around 1200 degrees on a two stroke. I'm sure the muffler itself runs a little less but still... I've tried silver soldering mufflers and had the solder melt and blow out. Also, I'm not sure what the trick is, but nobody I know seems to be able to make this aluminum welding that you see in the booths work as well as they do it for some reason. Brazing steel mufflers works, or else tig weld aluminum.

Just my experience,
AV8TOR