With a little investigative tinkering, I was able to get mine to work. It turned out to be the starter button. The button is made so that when it's pressed, it breaks the headlight circuit so the light isn't on while the starter is engaged. The problem with mine was that when the button was released, it came out too far and again broke the headlight circuit. I suspect this is caused by normal wear.
This is easy to trouble shoot. With your key in the "on" position, push the starter button in ~1/16". If the headlight comes on, you've found the problem. I fixed mine by epoxying a tiny sliver of plastic milk carton to the switch housing in the nook above the starter button where the button rests. This is hard to explain, so I can send pics if that would help.
Good luck with yours!