If the field windings aren't getting power, the generator should still put out 1/2 volt from the residual magnetism. If the generator output is an absolute zero, then the output might be getting shorted by too long a screw on the generator side of the cutout, or lack of insulators on the output post, or a broken wire, or a bad armature.
Remove the cutout from the generator and touch the battery cable to the generator output post of one second, then start the engine and see if the generator has any output. If not, then remove it and check inside for the problem.