I would guess either the float level is too high, needle and seats are sticking or have debris between them, or the fuel pressure is too high and over powering the needle and seat.
First off, check and set the fuel pressure, no more than 7 p.s.i. at idle.
Second, remove and clean the needle and seat assemblies, make sure they work smoothly.
Third, reinstall the needle and seat assemblies almost all the way down. Then, with the engine or feul pump running, set them to the point that the fuel barely trickles out of the sight plug holes.