Aloha,

I am looking at the wiring diagram for neg earth found in the tech section http://www.wdbsa.nl/download/808.jpg .
If I want to can I change it to pos earth just by switching the wires "A" and "E" and instead connect the "E" to the battery and the "A" to ground? (naturally polarizing the dyno accordingly)

Or will this mess up things with the regulator unit? Any other problems to be found?

/Simon

Simon you simply swap the wires on the battery to Poss earth and re-polarise the dynamo. But can I ask why you want to change it? Unless you are using a Poss earth electronic regulator? The mechanical regulator will work either way. No need to swap any wires round on it......You'll probably have a fire if you do Ron

email (option): ronpier@talk21.com

If you have a negative earth solid state voltage regulator you need to keep the bike negative earth. Some regulators can be changed easily from 6v to 12v (e.g. the DVR2), but you cannot change the polarity without changing the regulator.

The benefit of negative earth is that if you want to use LEDs, there is much more choice of headlight bulbs in negative earth; especially so at 12v.

The other benefit of negative earth is that most vehicles are set up that way so you don't have to remember which vehicle has which polarity and make the mistake of burning out wires when you reconnect batteries.

If it was me, I would switch the regulator to 12v, use a 12v battery and run the lights on 12v LEDs. There are lots of cheap 12v negative earth dip/full beam headlight and pilot light bulbs on the market (ebay will source the cheapest). Rear brake/stop lights tend not to be polarity sensitive (why, I don't know).

The dynamo will easily charge a 12v battery and the LEDs draw very little power.

Unfortunately, I didn't plan much, so I am stuck with a positive earth DVR2.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Thank you for your answers gentlemen!

The dynamo has been laying a basket (as have the rest of the bike) for some 20 years so it will probably be a case more of "polarazing" than "re-polarizing" the dynamo.


I am using a mechanical regulator. And the answer to you question is in the next reply that i got:

Most of my vehicles have pos earth. Sounds like a lot doesn't it? It really is just a Bonneville and a Vespa, where the Bonneville uses pos. and the Vespa AC and no battery at all.*

Another answer is that I also quite like the quirkiness of pos. earth.

I do not want to use LEDs, unless absolutely necessary. I find them to be a modern atrocity.

Now that's interesting! Can't help but wonder why the bikes were made with 6 volts to begin with? I now have a mechanical 6 volt regulator so I will stick with 6 volts for now. Until the regulator turns out not to function.

Was the M20/21 made with pos. or neg. earth originally? My real reason for posting this thread to begin with perhaps is that I was quite surprised to find a wiring diagram for neg. earth since I was under the impression that all old brits use pos earth.


Thank you again for your answers!

/Simon

*I actually also have a -84 Honda XR500 in baskets, that was given to me by a friend before he migrated to Uruguay to live off-grid in a hut. The bike has been stolen by Norwegian junkies and then found again so it needs a lot of work to be done to it.

British pre-war and wartime magdyno equipped machines usually had a -ve earth system. They changed to +ve in the early 1950s to follow automotive convention....and the car industry then changed to -ve in conection with radio supression...and once again it took the motorcycle industry twenty years to catch up and end up back where they started !

This explanation seems logical and fits in with what I thought I could remember...

http://www.rrec-northeast.co.uk/positive_negative.pdf

Good to know Rik!

Makes littles sense for me to build a neg. earth system it seems. Good thing I asked.

/s

And yet my WD vehicles 1940-44 all have wiring diagrams that show a Negative earth system.(Morris, Austin, Jeep, Ford etc) and of course all the bikes are Neg earth.

Ron

email (option): ronpier@talk21.com

Hrmpf... this should of course read "Makes little sense for me to build a POS. earth system it seems", not the other way around as it came out.

So it goes, as the great man wrote.
How am I ever going to get my mind sorted between my different vehicles one might wonder...

/s

I have a positive earth Commando as well. Keep a pack of fuses handy if working on the electrics is all that I can suggest !