It sounds as if the carburetor may be flooding. If you turn on the fuel but don't start the engine, does fuel run out of the primer bulb, or into the crankcase? If it does, your float needle is not closing off the seat, probably either because there is dirt in between the two, or (more likely) because you lost the tiny plastic needle when you took the carburetor to pieces and now don't have a needle at all.
