First... have someone constantly pump the fuel primer bulb, acting as a manual fuel pump. If this corrects the problem, the fuel pump is not performing properly.
Having the engine bogg down and die out indicates the engine is starving for fuel, not loading up. Did you manually clean the high speed jets (4) located in the bottom center portion of the carburetor float chambers? If not, do so as solvent really doesn't do a proper job on them.
Does the timer base move smoothly from full retarded position to its full spark advance position? If sticking, correct that problem.
If pumping the fuel primer bulb hard causes fuel to flow out of the carburetor throats, the float levels are wrong or the float needle valves are faulty. Set the floats as follows:
(Carburetor Float Setting)
(J. Reeves)
With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.