Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

One other thought here Jim ..... are you opening your gas valve all the way to the stop point every time you fire this boiler? If so, you might want to try turning the gas down a little, and then maybe the mixture will lean out and stop wasting gas out the stack. If that turns out to be the case, and you still want to use your gas control valve at max setting, then I would think the next smaller jet might be the way to go.