I have built and ran small i.c. carburetors originally designed by George Britnell and by Malcolm Stride. Both of these carburetors included "air bleed" screws in their design. Recently, I seen a post by George Britnell saying that he no longer used the bleed screws in his carburetor design. I myself have found that they don't seem to have much effect on how well an engine runs. They give a very small bit of influence on how the engine idles, but I question whether or not any improvement they may add will offset the bother of using them at all. I am soliciting opinions from other knowledgeable folks out there who have built and ran these small carburetors with "air bleed adjustment screws" on them.---Brian rupnow