the needle and seat in that carb is leaking, super flooded that cylinder. it may just have a piece of dirt in it,quick thing to try is get it running on all 3, switch the fuel shut off valve off while running, and try to catch it and flip the valve back on before it dies. the sudden surge of fuel may flush it out
Is the mag side where the impulse line to the fuel pump is? If so, you could also have a hole in the fuel pump diaphram that is filling the crankcase with fuel. To check that, remove the impulse line from the fuel pump, there should be no fuel coming out of the fuel pump via that line.