ichthos, I just went through this on a Zenith carb. You need to get a long allen wrench and stick it down the damper as you would to adjust the mixture (the tube you put oil in to dampen the the piston movement) I don't know the exact size, moss and other sell it as Zenith Stromberg adjusting tool.
You need to turn this counter clockwise (as you look down at it) unitil the needle is at its lowest, this takes the needle off its threads, then you loosen the setscrew in the side of the piston and the needle should come right out.
Be careful using a pliers on the needle, you do not want to scratch it it all.