sounds to me your messing around with an air bleed carb low speed screw when the HIGH SPEED needle is what is important. true , the low speed needs adjustment BUT the airbleed is often not as sensitive as many think. it is the TN two needle carbs with low speed MIXTURE control that are very sensitive. case in point; some air bleeds have to be drilled out the next drill size inorder to have any effect at all.high speed needle too lean.