A good technique to get close (with a true idle NV, not air bleed) is to put fuel tubing on the carburetor and blow in to it with your mouth. Do this with the throttle in the normal nearly closed idle position. this is when you can just barely see a small opening at the throttle. With the throttle set this way, you should be able to hear some air (from your breath pressure) passing thru the needle valve. You need to do this in a quiet place. If there is no air passing thru you are too lean. Open the low speed NV until some air passes through. This is usually a good starting point to get the engine running.