If you are sure the needle is in place, you may have put it in upside down - it has to go in point first.
To check what is happening, you could remove the main jet, pull out the float bowl cover (held in by the main jet), and see what happens if you turn on the fuel tap and gently lift the float. Fuel should flow when you let the float drop slightly, and stop completely with very light upward pressure on the float. If fuel keeps flowing when you gently lift the float until it stops, you have found the problem: flodding, due to the needle not closing off the aperture in the seat. If that happens, check whether you have put the needle in the right way around (point first).
