pilot screw- in or out

Hi! What do the pilot screws regulate? Is it airflow? Fuel ? Or mixture of the two. I’m confused. My plugs are always fouled w/ gas. I suspect the pilot screws adjusment has to do w/ this though I set them three turns out. I notice this when I rev my bike from idle to about 1/8th throttle openning, (bike is stationary) and it makes sense coz this is the range where these pilot screws are supposed to be regulating whatever is passing thru. Basing on the carb. diagram that comes w/ the FZR 400, these pilot screws are controlling the flow of air and fuel mixture.If it’s the same w/ the carb. of FZR 250, ( w/c I think is the same) then turning them in make the mixture leaner and turning them out make it richer. Am I correct? Now, I kept thinking, what if these screws control airflow only, it’s the opposite, right? Turning them in make the mixture richer and turning them out make the mixture leaner. And if it’s fuel, it’s logical. So, w/c way should I go to correct the fouling, in or out? I tried screwing in about a quarter but still fouled. Other causes? So far, I have cleaned the carb., set the fuel level, changed the plugs, checked the resistance of s. plug caps but still has to do carb, synching. Pls. shed light on the matter. Thanks. <!-- s:???: --><img src="{SMILIES_PATH}/icon_confused.gif" alt=":???:" title="Confused" /><!-- s:???: -->

 

Yeah, I thought of adusting the needle but it was a screwed- in on the throttle slider & there wasn't notch on it. Perhaps it came just like that (stock) so that it can not be tinkered w/ or the previous owner modified it. My bike is FZR 250 2KR (steel frame) model 1988.