B40 to 12v

[griffo]

How east is it to convert a B40 to 12v so that a Boyer ignition system can be fitted ?   Thanks

[chaz]

easy,
depending on year.
I also did negative earth at same time.
depending on which generator fitted , you would need to replace coil , bulbs, horn.

[Mike40M]

Agree, quite easy. Have a Boyer on my B40WD, which has 12V positive earth. Made a total rewiring on it.
I suggest you shall check on the electrical diagram for B40 and B44. I got the manuals from https://www.bsaunitsingles.com/owners_repair_manuals.htm
If you have a 3 wire alternator, it can be connected as a 2 wire one. Then instead of the now unobtainable Zener diode, best to replace the rectifier with a rectifier/regulator. The 3 wire alternators third wire was used to get more output with lights on. Only have to know which two wires to join. The Zener or a Rec/reg can make the wiring in the lights switch simpler. Of course you have to change to 12V battery, bulbs and coil. Some people says that the horn works on both 6V and 12V, Don't know. Some Norton folks says that the 6V condenser shall be replaced by an normal 12V external automotive condenser as Lucas had to upgrade when going 12V.
I have an capacitor AKA battery eliminator fitted which makes it possible to start without battery. Also fitted an Battery Status Monitor which I've found much more useful than the unreliable ampere meter.
I have found Paul Goff (http://www.norbsa02.freeuk.com/) and Al Osborne (http://www.aoservices.co.uk/) both helpful and able to supply parts needed.

[chaz]

as you want to stray from the original , concours is not a factor. try looking at a Japanese reg rec , modern tech , 2 from the generator, one to earth and one to the feed side , dissipates the heat better and is more stable.

[griffo]

  Thanks lads I've a 12v reg/rec in the shed so lets hope all goes OK...