Here's a way to get a preliminary setting on a low end screw when it is out
of whack. ( out of whack is a high tech term )

Close the barrel with a toothpick in it to keep it cracked open.
Put a length of fuel line on the carb inlet.
Blow through the fuel line and turn the screw in until the flow of air stops.
Open the screw until the flow of air starts again. (ccw)

That will give you a slight flow of fuel at the idle setting, and a good starting
point. From there, give it 1/8 turn at a time until you get it set. You can use
the "pinch test" to help get it set. Get the engine running at a fast idle, and
pinch the fuel line. If the engine speeds up, turn the screw "in" 1/8 turn and
try it again. If the engine just dies with out speeding up, it is too lean....open
the screw (counter clock-wise) 1/8 turn. You want it to speed up ever so
slightly when you pinch it (slightly rich).

A slightly rich setting on the low-end makes the engine easy to start, and
insures the engine will not over heat at low speeds from the setting being
too lean. Slightly rich is where you want the high speed needle to be as well.
Close the high speed needle until the engine is running as fast as it will go....
then open the needle until you hear the engine slow down a bit. That is the
slightly rich setting on the top-end.

FBD.