Original needles for both A and B carburetors can often be reseated by using a needle-nosed pliers to press on and rotate the needle. Move the needle position and rotate some more. I use penetrating oil on the seat while I do this. Some people rotate the needle with a drill while pressing, but I think that this would be a little rough. Some people tap on the needle to help re-seat it.
Make sure that the float is pressing the needle straight up and not to the side. About 70% of the needle valves will clean up with the above method. I use a hand-operated vacuum pump and gauge to check for leaks. This is the same pump that can be used to help bleed hydraulic brakes.
