'72 cooktop w/ yellow flames! Help!

[tphan]

Hi- my original '72 4-burner cooktop works well on 3 of the burners, but the 4th spews yellow flames. Up near the front of the unit, by the on/off valves, are baffles that can be adjusted, for air inflow, I guess. All 4 are adjusted about the same (1/2 open), and monkeying with it did not get rid of the yellow flame. Just in front of these baffles is a threaded, brass fitting, inside of which is a needle valve, of sorts. What function does this fitting serve, and what effect does either tightening or loosening this fitting have? Does it have anything to do with gas output/ mixture etc,? This faulty burner also does not readily light from the pilot, so something is amiss here. Could the fault lie in the burner itself, a disintegrated gasket maybe, or some other air leak causing the yellow flame? Thanks for any info!

[VIKING]

It could be from a loose burner, or the fitting where the pilot tube goes into the burner may have come loose. I'm not sure if yours is the same as my '64, but mine has a metal tube about 3" long going from the bottom of each burner to the area of the pilot light. The tube attaches to a brass or aluminum 90 degree "L" fitting that goes up into the burner. I had one of the 90's come loose and it caused the same thing you have described. The pilot would not light that burner and if I lit it by hand it burned yellow. It could also be caused by corrosion or a spider web in the burner tube somewhere. It doesn't sound like a simple adjustment gone bad. I would clean and inspect that burner before adjusting it.
Good luck, Rich

[centennialman]

The threaded brass fitting may be the culprit. It could be an "air mixer" of some sort. You might call an appliance repair place and run it by them.

I have an antique restaurant gas stove in my kitchen and the repairman taught me how to use the set screw to mix the air correctly for a blue flame.

Good luck

[Diesel1]

A yellow flame is rich (to much fuel, no oxygen) The little butterfly valve you mentioned is to let air(oxygen) into the fuel to get the proper air/fuel ratio.Maybe the tube under the butterfly valve is plugged and not letting the air into the fuel stream. Adios, John

[tphan]

Thanks, all- I will check everything mentioned in your replies.