1954 BSA B31 plunger electrics.

[briancairns]

Hi ,

Please accept my apologies, I am very new to BSA's.
Just bought a 1954 BSA B31 plunger. The bike starts fine and assume the magneto is working.
There are no other electrics on bike, so I am making up my own wiring loom etc. There is also no battery. The switch gear is present and so is the amp meter.
I need to purchase a voltage regulator /control box.
How can I tell if I require a positive earth regulator or a negative earth regulator?  And where on bike do i attach it to?

Is there anything else i require? headlight and brake light and fittings are there.

Many thanks in advance.
Brian

[idie]

If you are starting from scratch it doesn't matter as to whether you have positive or negative earth. Personally I would go for negative earth and 12 volt. You then have a good availability of choice over bulbs. Get a regulator from Dynamo Regulators Ltd 01489 880552. He advertises in the Star and is a BSA rider.You will most likely need to re polarize the dynamo. When you fit the battery take a wire from the F field terminal of the dynamo and briefly flash the wire onto the live terminal this will repolorize the dynamo.

[briancairns]

Thanks so much idie,

Again, please excuse my ignorance on these matters.....if the bike was originally 6v and the magneto / dynamo is the original (and appears to be working), do I have to stick to a 6v regulator and battery?

Thanks again

Brian

[Derek996]

Absolutely not, unless you are a stickler for originality. 12V gives you better lights and the convenience of being able to buy bulbs easily yet the bike can still look completely standard.

[Dean Southall]

I would support Idie's proposals. I have done this with my dynamo BSAs.
By the way your magneto is around 20,000v not 6v! Seriously, it is electrically competely self contained and independent of the rest of the bike's electrical system so you can always get home if the dynamo/battery fail

[briancairns]

Thanks so much all for your valuable advice.....12v it is!

Thanks again
Brian