Hello all

Hi my name is Hal and I'm 66 years old and own a Bultaco Alpina #116. I have been riding since 1971 and have owned the Alpina for 3 years. I am in the process of rewiring the headlight, taillight. The model year is 1974 and it has a Lucas hi-lo/ horn button combination switch. The headlight is also a lucas unit with red high beam indicator. I have run all new wires on the machine the resistor and diode tests good. Does anyone have a schematic for the headlight? There was also a small lucas diode bolted to the inside of the headlight bucket and that tests no good, was this diode original or did somebody add it in? Also the bike is still on points and condenser

I am familiar with lucas wiring and know which wires are Hi and Low.

I am trying to get it legal so I can register it, I certainly would not entertain riding at night with a 6 volt headlight. Thank you for any help or insight that you may have.

Thank Hal in CT.

I can't help you with the wiring but that picture is '' the '' real reminder of my first bike yes a 116 ( 160000295 ), its the first picture of an Alpina with the small push in gas cap and the one piece tank and side cover I see in a long time. Yours seem to have the '' banana '' exhaust as mine was equiped with the small triangle too restrictive one. A real nice bike congratulation.

Guy

4993 resistor would be 499 kiloohms I'm going to wild guess that makes a low beam happen and the rectifier would support a horn which requires DC.

... a resistor that powerful would almost kill all the voltage coming from the 6 volt system so not sure about the resistor purpose, the Bultaco schematic does show the resistor. Another diagram refers to a current stabilizer, the resistor would be to stop the bulbs from burning out and the rectifier is also needed to charge a battery if so equipped. Incandescent lights can operate on non rectified voltage.

Edited Friday at 02:35 AM4 days by lemur

The name and number codes on electronic components often help with their identification.

Thank you all for your replies.

the picture of the headlight shows the electrical item circled in red. It has lucas and #49993A and looks to be a Diode. I have checked it with a DVOM and it it doesnt read for a diode or a resistor. If anyone who has a mid 70s Bultaco with a Lucas headlight please take a picture and share it.

I have the 5 speed Bultaco manual and it has 2 wiring diagrams. Which isn't really clear on the headlight wiring and I don't seem to see the lucas 499934A item in it. the lucas 49934A was bolted to the headlight shell right above the hole in the headlight for wiring pass through.

Thanks Hal

Use an oscilloscope to test the power being supplied to it, that will give you a hint as to the components purpose. If it is a diode that's a bonus, easy to replace on spec. That would make it a power diode as it is designed to sink heat and the main purpose would be to roughly regulate voltage output to match the lighting requirements. If a VOM test fails in both directions the component must be cooked.

Thanks for the reply. I had looked up the diode and couldn't find any.

After searching for "lucas power diode 49934A" it comes back as obsolete, but did give me some modern equivalents. I had been looking up (lucase diode 49934A) putting the word (power) gave the information about modern power diodes

Thanks for the feedback. I really appreciate it

Thanks Hal

PS. I'd still like to see a picture of the wiring in a Lucas headlight if ANYONE HAS ONE.