Bridge Rectifier

[frankfast]

s-l640.jpg

If I convert to 12V, I happen to have this Saprisa R/R. I see where the two yellow wires from the alternator are connected but not sure where the red is connected. Which terminal would go to the battery, coil etc. Since I have this unit and if it works, changing to a 12volt system might be advantageous.

[ducwiz]

This R-R cannot be used to convert a single to 12 Volt. Afaik, it was made for the Mototrans parallel twins, but I'm not sure.
Internally, it is constructed like the genuine Ducati 12V R-R for the 750GT/S and 860 twins, for a 2phase alternator, where the alternator's red wire is the +DC output. As I described, you must use a 12V single phase R-R (or 6V if you stay with that voltage), connect the 2 yellow wires and leave the red one open.

Hans

[frankfast]

There are a number of single phase 12 volt regulators on Ebay out of the UK. Some by Podtronics, others Lucas. Some have 4 wires, two yellow, one red and one black. One even offers a battery eliminator, I think in the form of a capacitor, which would be a plus if it works. Is there anything I need to know about these offering?

[ducwiz]

Hi,

please read this thread http://www.motoscrubs.com/forum/viewtopic.php?f=3&t=3207.
Result of a quick search for "regulator rectifire 5wire" on ebay-uk: https://www.ebay.co.uk/sch/i.html?_from ... =0&_sop=15
Btw, 5wire means:
1 x red wire = battery+, 1 x green wire = battery -/chassis frame, 1 x pink/1 x yellow wire = AC input from stator (2 x yellow), 1 x black wire = regulator control input, +12V from ignition switch
There are also 4wire R-Rs. They can be used as well, but their disadvantage is the missing black wire. In turn, these R-Rs continuously might drain the battery with a few milliAmps. After several weeks of idleness, the battery condition can be low
Another source for R-Rs in the UK is Rex's Speedshop https://www.rexs-speedshop.com/product- ... ectifiers/. They sell two R-Rs which can be used with the Ducati or Motoplat alternator stators:
https://www.rexs-speedshop.com/product/universal-single-phase-regulator-rectifier-110w/
https://www.rexs-speedshop.com/product/motorcycle-universal-12-volt-regulator-rectifier/
But beware, the latter is a 4wire type! And it has a significantly higher and hence unnecessary power rating.
Finally, here is the Electrex Universal 6/12V R-R (4wire!): https://www.electrexworld.co.uk/cgi-bin/sh000001.pl?WD=universal%20regulator&PN=RR02%2ehtml#SID=439

cheers Hans

[frankfast]

That's great. There seems to be multiple options. Thanks so much Hans.

[Scottish888]

I fitted a new chinese 5 wire regulator/rectifier to create a 12v system.
reg/rec loom
Black - Brown (named marrone on logitron)
Pink - yellow
yellow - yellow
green - battery earth
red - battery positive

I noticed the bike would start and run with the battery +ve disconnected. The engine cuts if turning the ign key off.
Should it start if the battery is disconnected?
It is charging the battery very well, over 14v.

Regards

[frankfast]

Ducwiz - If I'm using a simple toggle switch to send voltage from the battery to coil and lights, where would the back wire from the 5 wire R/R be connected? I took your advice and purchased a cheap 5 wire R/R from China. Going to be a bit of a wait to get it. Thanks for all the help.

[ducwiz]

Scottish888 and me have already explained where to connect the black wire: make a connection to the brown wire from the loom, which is presently unused. This wire starts from the +terminal of the ign. coil. It shows pos. voltage when you operate your key switch (see schematics).

Screenshot - 25_05 003.png

cheers Hans

[frankfast]

That's the problem. I'm not working with the original loom. My harness is home made and nothing like the original. I don't have a key switch but rather a simple toggle switch with a connection to the battery on one side and a connection to the coil and lights/horn (via fuse box) on the other. Do I still need the black wire and if so where would I connect it?

[frankfast]

Connect to the positive terminal on the coil. Thanks, got it.