Do most Alpina Model 85 riders use the stock electrical system or toss it for a total loss battery system?

Most either use the standard points or put a CDI system in them.

If you want to run lights, a total loss (12V battery) system running LEDs is a popular (cheap) option. The standard lighting supply is only nominally 6 volts and the voltage is highly RPM dependent. At idle and low RPM the standard lighting is very poor.

However for the ignition electrics, there's nothing wrong with the standard points/coil system design/equipment.

Thanks, feetupfun.  I must have lights to get street legal where I live, but I don't expect to ever be riding at night.  Sounds like the stock electrical system would be acceptable for me, and it would keep things simple.  However, to get the stock system functional I will need a brake light resistor, and I've had a TOUGH time finding one.  Lorenzo mentioned in a post several months ago that he found a couple on eBay.  I've been watching since then and have not seen even one come up for sale.  None of the parts suppliers I normally deal with offer a resistor.  Do you have any ideas for me?  Alternatively, can you tell me how the circuit is arranged and what the diode capacity is?  I can buy a resistor and a diode and mount/wire them to make my own if I knew the arrangement.  Thanks again for your help, feetupfun.

20 hours ago, LSMO said:

Thanks, feetupfun.  I must have lights to get street legal where I live, but I don't expect to ever be riding at night.  Sounds like the stock electrical system would be acceptable for me, and it would keep things simple.  However, to get the stock system functional I will need a brake light resistor, and I've had a TOUGH time finding one.  Lorenzo mentioned in a post several months ago that he found a couple on eBay.  I've been watching since then and have not seen even one come up for sale.  None of the parts suppliers I normally deal with offer a resistor.  Do you have any ideas for me?  Alternatively, can you tell me how the circuit is arranged and what the diode capacity is?  I can buy a resistor and a diode and mount/wire them to make my own if I knew the arrangement.  Thanks again for your help, feetupfun.

If you want to do it the original way, from memory there are wiring diagrams in the owners manual and in the generic 5 speed Bultaco service manuals.

There are also wiring schematics on this website : -

Here's one I posted earlier (this is a scan of the appropriate page in the owners manual)  :-

This is not very clear ; here's another in Spanish that you should be able to make sense of :-

Says Sherpa T, but wiring is exactly the same.

Hope this helps.

Edited April 30, 20233 yr by lorenzo
clarity

Thanks, Lorenzo.  The Spanish schematic gets me closer but I'd still like your confirmation that I understand it properly:  It looks to me like the diode and the resistor are wired in parallel and the negative (cathode) side of the diode goes to ground.  Yes?

If so, do you have any idea what the wattage rating is for the 4.7 ohm (from your post of 22 Jan) resistor and also for the diode?

If I am following this correctly, the diode plus resistor you mention make what is a basic voltage regulator as used on various small motorcycles.  Its purpose is to limit voltage to the lights so they do not fail.  Something like this:

https://www.rexs-speedshop.com/product/universal-6-volt-ac-regulator/

Thanks, mcman56. Can't see why universal regulator should not work on an Alpina.

LSMO  - I don't have any accurate means of measuring  resistor/diode performance. Is polarity an issue ? - this is AC, after all.

Additionally, if I understand its function correctly the resistor/diode affects only the stoplamp / LT igntion coil circuit. I believe there must be other ways to provide a stoplamp : LEDs and a small battery, maybe ?

I used something similar on a DT175 with 12 volts.  It came without any kind of regulator and would blow up bulbs.  This basic type regulator cured that issue.  We had some kind of variable AC voltage generator at work so I hooked it up to see how it worked.  It did nothing until about 13.5 volts and then interacted to hold the voltage down.  I guess the diode "opened" at 13.5 volts and sent excess power to the resistor that dissipated it as heat. 

Can't imagine how I would have gotten very far through this restoration without help from folks like you.  Massively appreciate all of your advice!

Do any of you have experience dealing with guzman175 who is offering FEMSA RSA1X-7 that look like factory original pieces?  guzman175 is shipping these from Spain.