In the figure above, pay attention to #75 and #76. In "Low" position #76 orifice is near closed. More air less fuel enters the generator. I've included the patent number for your convenience. You may find every detail you need there.
That procedure will not help to clean the rust or other contaminants coming from the tank. Simply these are not combustible. I have learned how to fabricate my generators, in less time that is required for cleaning trials, I own a perfectly new generator.
Yes, in "Reborn 400A stove" topic in this forum or CCF "Collections: Restored Pieces and Before & After Projects" I explain in more detail the steps with pictures.