Intermittent headlight

My '86 VFR750F seems to specialize in idiosyncratic, intermittent electrical malfunctions. The latest is the headlight, which sometimes does not work at all. Oddly, when I take it all apart to check various possibilities, it works. It does not seem to be the contacts at the headlight itself, and jiggling the hi/lo switch has no effect on it being on or off, but works perfectly to change the beam. Is there some relay in the circuit that could be failing, or have bad contacts? I have tried following the wiring schematic and do not see one, but my abilities there are limited (as is the resolution of the schematic I have). Does the starter relay, for example, turn off the headlight while cranking? I would be most grateful for ideas and suggestions.

 

The START pushbutton turns off the headlights while cranking, and dirty contacts there or a weak return spring or a broken solder joints can cause headlight intermittency.

 

That sounds like it could be it. I noticed that it tended to be either on or off when I started the bike, rather than switching when the bike was running, which is why I was thinking the starter relay cut the headlight. This is simpler. I can take that switch apart to clean the contacts?

 

Best to use a spray of contact cleaner around the switch as access to contacts is limited, i believe.

 

I'll try that. Is that the likely spot for a bad solder joint too, do you think?

 

There's a sprong inside the starter button thats prone to wear. If t doesn't fully spring/push the button back up, the headlight wont come back on after you start your bike. I've seen threads on here that describe how to do the repairs yourself.

 

Thanks for all the help. The diagnosis was spot on. I took it all apart. Cleaned the contacts. Removed a bug egg sac. And now it works, and even allowed me to ride home through the night.