Once the high speed is adjusted, slow the engine down to the point where it begins to falter. holding it there, pinch the fuel line with fingers or needle nose pliers (be careful of prop at all times)(this will LEAN the mixture) if the engine accelerates a little before quitting then you are too rich. If it quits immediately, you are too lean. Adjust bleed screw accordingly and try again lowering speed every time until you get idle speed. It is a balancing act but it can be done.