Running has a constant beat or rythim of the flame...

Question

I have run this for a while and found that some one has been playing with the compressor screws. I dont know where the compressor screws are soposto sit ( 1 1/2 turns for example). I have cleaned the tank and put new fuel filter in and still dose it. It sounds very rythmic all was at the same time. sounds like the flame gose out and then comes back and has to catch up with the fuel in the camber. I looked at the spark plug don't look bad but what could cause this to do it the same amount a time between times.