I have replaced coil, plugs, points, condensor, rotor, and battery. When I turn the ignition key, there is a spinning, whirring, kind of clattering sound, like dragging a stick on a picket fence, but it doesn't turn over. What might this be? P.S. I also reworked the starter, including a new gear at the end, which worked the first time I tried it but hasn't since. Thanks for any help or ideas.