+ ve or - ve earth?

Hi Paul, My pre 1953.singles and twin are all negative earth and my Commando and featherbed Dommi and Es2 are all positive earth. I don't see any differences in plug life or points wear with either system.

regards Ian

I like negative earth as it's the same as other vehicles in the family and my ageing brain is very easily confused.

Paul has raised a very important point with his posting. When I bought my 1948 ES2 I had no idea whether it was positive or negative earth. I rashly assumed it was positive like all of my Dominator bikes.

The wiring diagram in the manual did not really help as it shows the battery wire colours but not the polarity of the terminals they connect to. See attachment.

Somebody call Al Oz and ask for some guidance on this very important matter.

Interestingly, my older bikes (Velo, Rudge) are negative earth but my newer ones (Norton, BSA) are positive earth. The very first Land Rovers were positive earth but thereafter all were negative earth. The universal standard now is negative earth for vehicles. It would seem that there is an argument in favour of negative earth for marginally reduced corrosion but frankly I don't see any discernable difference.

What is scarily amusing is when jump leads are used between a positive earth vehicle and a negative earth vehicle and the two are touching bumper to bumper (has to be metal bumpers of course).

Flashing the dynamo and swapping battery leads is pretty much it - unless you have a solid state voltage regulator which would have to be changed.

Al Oz here. All the above is correct so far. But please look at the pdf on my web site via the big Orange Icon RHS. Your last words are correct Gordon BUT you forget the colour of the wiring especially earth wire. Yes by re-polarising the Dynamo and turning the battery around it all works. Next time you reconnect the battery the wrong way round you could find your electronic regulator turns into a puff of smoke. The mechanical regulator will change polarity and it has even been know for a bike (Mech reg) and battery to change its polarity, and nobody knew........

The thought that you have 6 vehicles neg earth and you don't want a 'rouge' in them so ALL are neg earth is a very good point. But do be aware of the next owner of the vehicle he might expect Pos. and you have it neg. so the CORRECT wire colours will help.!

The diagram mentioned above is very bad, as you say no polarity.....

The change to pos. earth came through in the 50s but was subsequently found to corrode copper radiators...but on a motorcycle? Certainly there is a case to reduce (pos.earth) corrosion. I have half a theory on this polarity change, but not to put it into words or some bozo will start to believe it...In the mean time is there any one about who was in the motor industry in the 50s who might know the reason for the change?

Al - I am assured by my elderly motorcycling/motoring friend (92+yrs) that we went positive earth in the early '50s in the UK to satisfy the American market which expectedit or demanded it for the export market. A bit like wrong side gear changes...it's all their fault.

He also suggested that he thought that positive earth was supposed to be worse for battery terminals - which would of course apply to motorcycles.

Presumably the US motor industry eventually woke up and changed their ideas.

Previously ian_richtsteig wrote:

Hi Paul, My pre 1953 singles and twin are all negative earth and my Commando and featherbed Dommi and Es2 are all positive earth. I don't see any differences in plug life or points wear with either system.

regards Ian

Here's the wiring diagrams showing pre 1953 negative earth and post 1953 positive earth. This may help members.