RE: New to Gas engine question
^^^I agree, The carb has a diaphram inside it that works off of the crankcase back pressure and acts as a fuel pump causing it to suck the fuel from the tank, so a clear vent line is needed in order for it to pull the fuel from the tank. The only lines you will ever see on a gas burner's muffler is a oil line for smoke. Also, when fabricating a muffler, It will effect the running of the engine just as a glow engine. Prolly will have to tune the carb once you have it done. Hope this helps.