I found something similar to this topic, but they really never answered the question. I have a 10hp OHV Briggs stratton Coleman 5500 generator. I took it camping this weekend and Iam drinking my beer and notice that the muffler is glowing orange,just on top where the head pipe enters it. The generator is running fine, no missing, starts first pull. Now it has stickers all over it claiming it runs lean for California emmissions and passes all these clean air acts and such(I got in a trade for a shotgun) anyway. Iam wandering is this supposed to run hot to burn off emmisions or what. I have had the generator awhile and it might have been doing it awhile and I never noticed. My first guess was that my cocoktions of Marvel mystery oil, stabil, sea foam, Shell 93, 32:1 premix(if its leftover and smells like gas it goes in the generator, may have created a jet fuel type mix. Anyone else every have this?