Headlight problem '84 VF500 Interceptor

When I turn on key, headlight won't work. Sidelights, turn signals, horn, parking light are ok; bulb and fuse are fine. The starter button is not working as it should; pushing it straight in no longer works, but contact(and start)can be made by pushing up on it. I asked some friends to check it out, but no joy; I know starter button is designed to briefly cut lights out when engaging starter, and it's been suggested that this is the source of problem($80 part). Would solenoid be a possible source(bike runs fine other than no light)?

Thanks in advance!