Change of polarity?

Obviously my Commando is positive earth, my other bikes are negative earth, as is everything these days, cars, vans etc.etc.

can the Commando be converted to negative earth, has anyone done it, is there any reason to do it, or to not do it?

I am aware, having done it before in the distant past on something I owned, of the need to swop over coil leads - but whatever else it was I did I’ve forgotten.

Thoughts?

Been done. No biggie. Gotta change out the rec & zener(s) and change the wiring a bit. Since all the bulbs are not polarity sensitive, they will work with electrons going either direction. The points/condenser setup might need thinking over a bit but switching to EI is easy and they can be connected for +ve or -ve grounds.

I have a commando and at one time as well as a 74 750 ducati gt.The ducati had spagetti wiring but an alternator which put out a similar output as a british one. One winter I made up a wiring harness .It went from neg to positive .Just used the british parts so like tornado said just be sure the parts are neg. The alternator does not care. The ducati worked perfectly after that.

Very easy to do
I changed mine to negative earth a long time ago
But I have a honda reg/rectifier
I changed mine to make use of polarity sensitive LED light bulbs and I thought my Koso exhaust gas analyser needed negative earth
Since then I found I didn't have to
Why do you want to change?

No I’m not wanting to change it. Perhaps if there was a benefit to doing it then maybe. The polarity issue caught me out on my T100C when I was looking for LED bulbs. I was asking more for curiosity sake.

Some LED's can be obtained which are polarity independant. Looks for that designation when ordering.

Digging in the history of positive versus negative earth in cars is quite amazing. But for a motorcycle both works well. If you aren't a rivetcounter, and have to replace the rectifier or a hard to find zener diode, the logical choice is to replace both with a regulator/rectifier. Then you are free to choose. The battery and the 2MC capacitor must be connected accordingly. The ignition coil(s) is marked plus and minus. Most electronic ignitions can be used with either. Check installation manual on wiring.
Only reason I've had for changing to negative ground on one of the bikes was an addition that needed it. As already said LED lamps might be a reason.
Only problem I've had was that the clamp for the ignition timing strobe light had to be upside down.

Really simple to do. Place some red & black sleeving onto the battery wires so the new configuration can be easily identified

I switched mine years ago for the sake of being able to use standard automotive LEDs and solid state flasher relay. That was before dual polarity LEDs were available. With solid state r/r it's simple, with zeners you would need opposite polarity diodes (actually easier to get than positive earth zeners). Wiring for ignition must change accordingly. Only down side to me is that the red wires in my harness are now negative.

Thanks for the replies. This is purely a hypothetical question for now as it’s all working as it should. I have a polarity correct sidelight for now, I’ll do the others when I can be bothered. I only wondered if there was a “scientific” reason why everything these days is now negative earth.

if I later decide to go for a current (pun intended) solid state regulator then I’ll consider swopping, until then it’s all fine.

Well I never! I was about to start a thread to ask almost the exact same question again. I’d forgotten all about asking it a year ago - I’ll tell you what, this dementia is a bitch when you get it

I wonder what I’ll ask in another years time?

Sux to get old.

Very true, but as my old dad used to say ‘it’s better than the alternative”

As you never really had an answer here, are you still asking the same question? I can take a wag at it.

Please do.

Since I posted this question I have installed a new wiring harness as the other one was grimy and tatty and a new one was peanuts.

in addition I have ready to install a Pazon ignition system and a Pazon voltage controller - it was time for some toys

Both of these can be installed either way round. So it will be interesting to find out what things I’m likely to forget to do if I do decide to do the change.

Swop battery, obvs - re sleeve the 2 cables and label them.
Remove zener diode
Re-do my extra earths I’ve run from coils and head in black not red.
Coils will need polarity swopping, but I’ll also have the Pazon kit instructions to ensure i get +ve and -ve hooked up right.

OK -

If you research earth ground you'll find that the term came to exist with the advent of the telegraph. Using the earth as the return path for the signal allowed communications with just one wire. Vehicles are isolated from ground via rubber tyres, but the old term persists even after a couple hundred years.

All searches on ground polarity will include references to galvanic corrosion, a process where two dissimilar metals in contact will erode in the presence of an electrolyte. From what I've read it seems that making the chassis positive makes the metal of the vehicle the "sacrificial" material, while making it negative makes the copper wires and connections the ones that corrode the most. The Brits, Ford Motor Co and many others chose to use positive ground for that reason, while GM chose negative earth. With the availability of high current rectifier diodes in the 60's everybody switched from dc generators to ac alternators and somehow the manufacture of that centered on negative ground (probably GM's influence on the market). So says the web, and the innernet doesn't lie

Today, the standard polarity of the stud on a stud mount power diode is the anode, which on a zener would be negative. They are readily available from electronics dealers, and if you want the "reverse" polarity for positive earth it's special order.