I have an old range. The burners go out before they are in the off position. There seems to be no adjustment screws on the valves when I take the knobs off.

There is some sort of gate that let's more or less air in as you open or close it. That is located at the beginning of the tube for the burner, right where it slides over the gas valve.

When I adjust this gate it does effect the flame but does little to help the issue.

Is there anything I can do? Or is this just how these old ranges were and I need to learn to modulated the flame manually to get it low without going out?

Thank you!