Can you not fit a later headlight from a 79, even if you have to fit the shell too surely thats better than these sealed beam units. You can buy the bulbs in packs of 5 i think and that way they aren't expensive. They are 35w too which should help keep the voltage in check.

You are getting 8.5v with a 17w lamp so if 25 will bring it in on spec which we expect you should still be safe with 35w. Maybe it will take an extra half of one volt. But you will have a better headlight into the bargain. And spares will fit in your pocket.

Have a look, surely that will be a straight sap with the sealed beam?

Clicky

I like that idea. I wonder if I can just find a conversion headlamp assembly that will accept cheaper bulbs but fit into the sealed beam shell. The sealed beam ones aren't too expensive. $10 each...

OK if that diode is connected to the kill switch is there to aid the kill function.

I like that idea. I wonder if I can just find a conversion headlamp assembly that will accept cheaper bulbs but fit into the sealed beam shell. The sealed beam ones aren't too expensive. $10 each...

I'm thinking the later headlight assy like the one in the clicky link would fit pretty much straight in. It does seem to be uses in a lot of Yam bikes through the seventies.