The black knob is the idle speed seting, if you have it too low it will not idle, BUT it should still run if you hold the throttle open some.no offense taken. i did forget to turn it back on at first but i realized that then turned it on. i put on just the main. i got mad and quit and went out last night. i have been reading alot on this this morning and i think i turned the wrong thing for the fuel air screw. what is the black knob that you can turn by hand with a spring on the knob?