1951 Model 18 earth

Assuming the bike is fitted with a magdyno, I would expect it to be positive earth. Having said that, with any dynamo it is a straightforward exercise to reverse the polarity, an exercise which may have been done by a previous owner. It is simple enough to remove adynamo and motor it - that will let you know what the polarity is.

The wiring diagram of almost any dynamo fitted bike would do the trick - ES2, even early Dominator for instance. The advantage of the dynamo wiring is its amazing simplicity. A good thing!

Hello Gordon,

Excuse me being picky but how does motoring a dynamo tell you its polarity? As soon as you apply power to it that dictates the polarity from tha moment on, it either, changes it or it stays the same?

The wiring of these bikes is so simple-the back and front light go to the light switch (the front via the dip switch) The battery feeds the horn and the stop light which in turn feeds 'the other' back light. The regualtor output feeds the battery via the ammmeter, the light switch is fed from the ammeter, which in turn is fed frm the battery. Job done.

Al Oz

I bow, scrape and grovel to your superior knowledge Al. As indeed I should. Being a simple soul, I reckoned that if you did the old twisted wires to the dynamo leads and applied a battery to them plus earth, if it motored the same direction as it would turn when the engine is running, the polarity would be correct for the setup, whether positive or negative earth. Am I wrong? Probably...

To answer your question, the 1951 single, and I dare say, all the other models of that year, is wired negative earth.

Since you are doing an electrical re-build, motoring the generator is part of the process to ensure it's up to scratch, AND, fitting a modern electronic regulator!.......hell, I've said it, now waiting for the purists.

Electronic regulators - wonderful things - and Al Oz has them in stock. Of course, you can hide them inside the shell of an old cvc unit to pretend you haven't crept into the 21st century. Even I have resorted to such chicanery...

Previously Gordon Johnston wrote:

I bow, scrape and grovel to your superior knowledge Al. As indeed I should. Being a simple soul, I reckoned that if you did the old twisted wires to the dynamo leads and applied a battery to them plus earth, if it motored the same direction as it would turn when the engine is running, the polarity would be correct for the setup, whether positive or negative earth. Am I wrong? Probably...

No need to bow and scrape, just buy the next beer!

Right then, motoring a dynamo, I understand itwill turn one way even if you reverse the battery that powered it? (open to confirmation) But what is sure there is no need to remove the dynamo to polarise it, you just remove the two dynamo wires and connect the 'LIVE' side of your battery to the Field. This assumes your battery is on the bike and is connected as it would be used. Job done.

By the way checking that a dynamo motors does not assure you that it will charge, but of course if it doesn't motor then it won't charge either.

Al Osborn (again)

PS I do a nice line in modern electronic regulators but then perhaps I shouldn't be advertising, let Gordon doit. Ta.

Previously alan_osborn wrote:

Previously Gordon Johnston wrote:

I bow, scrape and grovel to your superior knowledge Al. As indeed I should. Being a simple soul, I reckoned that if you did the old twisted wires to the dynamo leads and applied a battery to them plus earth, if it motored the same direction as it would turn when the engine is running, the polarity would be correct for the setup, whether positive or negative earth. Am I wrong? Probably...

No need to bow and scrape, just buy the next beer!

Right then, motoring a dynamo, I understand itwill turn one way even if you reverse the battery that powered it? (open to confirmation) But what is sure there is no need to remove the dynamo to polarise it, you just remove the two dynamo wires and connect the 'LIVE' side of your battery to the Field. This assumes your battery is on the bike and is connected as it would be used. Job done.

By the way checking that a dynamo motors does not assure you that it will charge, but of course if it doesn't motor then it won't charge either.

Al Osborn (again)

PS I do a nice line in modern electronic regulators but then perhaps I shouldn't be advertising, let Gordon doit. Ta.

Sorry to butt in here, Im doing a 1957 model 19s, just to confirm...positive earth?..yes?

I will be in touch soon Mr Oz, I think I will be needing a voltage regulator.

cheers

John

Me and my Dad both have the AO regulators fitted in all our bikes, Dad even converted his 1920 Henderson dynamo from 3 to 2 brush and fitted one. They are excellent pieces of 'fit and forget' kit and Iwould reccomend them to anyone.

Incidently I wired my ES2 up for negative earth simply because my Royal Enfield is negative earth, saves head scratching trying to remember which one is which if Iget caught on the roadside doing anything. I'd carry on using negative on any other bikes I do now for the same reason.

Cheers

Andy

Previously john_hawden wrote:

Sorry to butt in here, Im doing a 1957 model 19s, just to confirm...positive earth?..yes?

I will be in touch soon Mr Oz, I think I will be needing a voltage regulator.

cheers

John

Hi John,

My 56 19S is pos earth, although I have no way of being certain that's how it left the factory. The wiring loom does look very original though & all other Nortons of that time frame I have or have worked on have been pos earth.

Regards, Tim