Topic: Headlight burning out issue

[JoeBud]

I recently acquired a 1979 Honda XL100s.  The low beam on the headlight was burned out, but the high beam worked. I just replaced it tonight and the low beam lit up for a few seconds and then burned out. Again, the high still worked. I know have two headlights with burned out low beams. Thoughts?

[CycleRanger]

Could be a bad voltage regulator.
Check the wiring and check the VR and the voltage at the headlight with the bike running.
Headlight switch switch might have issues as well.
The good news is the wiring is super simple and the VR's aren't hard to find.

These old 6v systems are pretty anemic.
Even with a fresh battery my XL250 will barely run the headlight and the blinkers at the same time..

[Bigsam302]

I agree with CycleRanger and I know this from experience. Replace the Reg/Rec NOW!  I had my low beam burn out twice. And then after replacing it a third time, my bike completely shut off while I was riding around the neighborhood and my anti-gravity battery burned up. Luckily, my bike is all steel and it didn't damage my seat hump. See my build for pics and info.

Sam

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[JoeBud]

Thanks for the info. Am I good just getting a used OEM one or a newer aftermarket one?

[b52bombardier1]

Not sure this bike has a voltage regulator. Perhaps, it is like my older 70's bikes in that a healthy battery well connected to the electrical system is the voltage regulator. Basically, excess current gets dumped into the battery and bike lighting to control high voltage.  At idle, the battery is there to provide power.

These bikes have a primitive Dynamo permanent magnet system completely unlike the later bikes with a powered field coil.

Running a replacement rectifier from Radio Shack,  DigiKey or Mouser is also far superior to the original Honda rectifier.  I can give you part numbers if you want - around 5 bucks each. Some soldering required so keep your old rectifier wire harness.

Rick

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[JoeBud]

Thanks guys. Yes, it does have one. For now, I just ordered an OEM regulator. Wanting to keep this bike as correct as possible.

[CycleRanger]

Dunno about the XL100, but my XL250s has a regulator.

[strynboen]

is the rear bulb the correkt watt..and battery konnekted..to stabilice the voltage..you can Mount a one vire regulator on the light vire to the rear light. or instrument light.it vil stabilice the vhole light system..turn all over volting back to frame/negative

[JoeBud]

Thanks again for the info. Would a bad regulator also be the cause of by turn signals not working at high rpm's. They work great at an idle, but seldom come on while running down the road.

[CycleRanger]

Possibly, however I'd go through the wiring and check/clean all the connections.
Replacing the blinker unit would be a good thing to do as well, if you can find a 6V solid state even better.

[JoeBud]

Well, I tested my current regulator based on the instructions in the How To section. It tested out OK. I do know the bulb in the tail light is not correct. I have one of those coming. Thanks again.

[JoeBud]

OK, I checked the voltage to the low beam with the engine running and it spikes up to 26 volts. Again, I checked the rectifier and it seems to test out OK. Of course I have a replacement coming and I will test it as well to compare. I did order a new battery given I do not know the age of the one that came in it.

[strynboen]

mine cd 50(1972) have a konnektion in the light kontakt..vho gives a smaller battery load ,vhen the light are on..its a vhite/ yellow vire..if it are Loose or diskonnekted it vill give heigh voltage in the light system..if you turn the light off..the battery gets the full load..some Yamahas had a restistens build inn to take over volting. use a mekanical system
.så some sub systems is used to hold a stabile voltage.
..
.but after the elektronic ones is used, itS all is simpel and easy..to kontroll it..so a upgrade to a transistored stabiliator..is the easyest vay..more simpel and gives a better resultat.
.even it not are stock..but as long you not hack in the orginal viring..it can be done back..and no harm is done