68 250 Scrambler - Stator and Wiriing

[Rbranst]

My 68 250 Scrambler came to me with a small regulator and some homemade wiring.
The Stator has two yellows and a red. The Red has been cutoff. The two yellows feed a small 4 terminal regulator.
Am I safe to assume with the red stator wire cut it has been converted to 12V? The regulator is a small little no name silver box.
The Stator/flywheel is a Ducati Elettrotecnica 31.44.91. Does eliminating the Red suffice for 12V? As to the Regulator box and the rest of the wiring, I am redoing the wiring now that I have the correct headlight/speedo in my possession but I am wondering if I try to take this back to 6V with the proper regulator or wire it all for 12v and get a known modern 12v regulator. I have a brand new Yuasa B38-6a for this bike and am just now realizing it may be 12v. Thoughts? What would you do?

[mrkprsn]

I believe that your bike is still 6 volts. I also think you have to modify the stator's internal wiring (like unground the ends of the coils) to change to 12 volts. Search this site for that info.

Do you have a widecase? They came out in 1968. If so the three stator wires go to a five wire RR, The two other wires go from the RR to the battery and the ignition switch. I think the PO replace the original RR with a simple 4 post (4 diode) full bridge rectifier. It might not be a regulator.

The original RR will convert the voltage from AC to DC and drop the voltage to 7v+. Your current rectifier will only convert to DC but maybe not regulate the voltage so the voltage might be too high.

The only way to found out is to start the bike and test the voltage output with a multi-meter. Here is an original wiring diagram. https://www.flickr.com/photos/galpalu/3446755909

[Rbranst]

Yes it is a 1968 crossover to widecase model.
I have done some research and was still confused, there seemed to be those who claimed simply dropping red can be done for 12v, so based on the chopped off red and small box I assumed that is what is going on. I need a battery to start the bike though and had purchased a B38-6a but then realized I needed to see if the bike was really still 6v

[mrkprsn]

You may be right with the widecase system. The two authors of this post are no longer on this site but are/were extremely knowledgeable.

Have you read this post? viewtopic.php?t=1471

[Rbranst]

Yes - I was still a bit confused.

[Jordan]

On my widecase single, I disconnected the red wire and insulated it.
Now the output from the two yellow wires are used to feed a 12V system.
It is likely that your unbranded rectifier-regulator is a 12V type, otherwise why would your red wire have been disconnected?
Can you check what's printed on your bulbs?

You can use your newly bought 6V battery if you have an original type 6V rec-reg, and reconnect the red wire as standard.
And change all your bulbs back to 6V if needed.

[mrkprsn]

I forgot to add, can you tell if the sparking coil and the headlight bulb are 12v? If you think they are 12v then i would use any 12v (car) battery to connect to the ignition switch (youneed to turn the bike off) and then to the coil. After starting the bike, I would then test the DC voltage and amp output from the rectifier (it might not be a regulator) and the AC voltage and amps from the stator. With those results you should be able to figure out if what you have will suffice.

[Rbranst]

Great advice, thank you !

[Rbranst]

The original widecase stator is a two phase system 6v, 60-70 watts or something like that.
Question - if the red is disconnected, is this now a single phase 12V or is it still two phase.
Reason I am asking is, I am going to get rid of this bridge rectifier and replace with a nice modern RR from Ricks.
Am I now (with the red disconnected) looking for single phase or still 2 phase?
Can anyone recommend a high quality regulator for this situation?

Yes I have read all of the posts, seem to understand most of it, however I wasnt able to determine if I now am single phase or still dual. School me please.

[Jordan]

I don't know what 2 phase means.

But I believe the original wiring arrangement in your Ducati alternator is called single phase, centre-tapped. It has 3 wires.
With the centre wire disconnected, it becomes plain single phase, with 2 wires active.

As the centre-tap system allows full rectification with 2 diodes, whereas the 2 wire version needs 4 diodes, it may be that using fewer diodes was the aim with the 3 wire system.

So both systems are single phase and can be rectified.

You should expect twice the voltage when the centre wire is not used.
Good idea to use a new 12V regulator/rectifier with it.

I use one made for a USA designed ride-on lawnmower engine on my 750GT. It works well with the upgraded high output (amps) alternator.
I use a Lucas zener diode regulator and radio shop rectifier on my single, because I didn't know about the mower option at the time I did it.
It also works fine. Everything functions, despite having no battery.