What are you calling the muffler.... and what are you calling the silencer? This should model should have a bolt throug the center lengthwise with a nut at the front end correct? Are ou saying the back end is rotating on the fixed portion attached to the engine? If it's not tight you could be having back pressuer issues and that could cause the flameouts. Are the nut or threads stripped on the long rod running through it lengthwise?