approx 20 year old Boyer Branson

Hello Clive, next months Roadholder contains an article about converting to negative earth and includes details about Boyer EI in such a system - this may help.

The Boyer site has installation instructions that cover both + and -ve earth, this BSA / Triumph one has the negative earth as 1979 onwards triumphs were -ve earth.

http://www.boyerbransden.com/pdf/KIT00052.pdf

if the Ignition about 20 years old, I would replace it anyway.

With the latest Boyer or something else, there are many manufacterers 

With the old Boyer it was dificult to set a proper Idle 

I do not see any reason to go to negative earth since there are noadays also LED for

positive earth.

Of course you have to rewire the Ignition when the polarity is changed and
do not forget also the Rectifier/Regulator.

I have Commando MK3 still positve earth and LED.

Ignitions

Lucas Rita 1977-2001

Boyer Micro Mk3 2001-2014 (no issue except pickup wires)

Trispark (Second unit first failed, now with robust enhenced Version)

Marcel

Can make life easier. If, like me you have other bikes which are all negative earth, it can make sense to have the Norton wired up the same. It makes sense to me anyway. Avoids having to think too much when refitting a battery.

I was 'lucky' when I got my Dommie as there was no wiring or electrical components with it, so I started with a clean sheet, hence my bike has a Kawasaki sourced regulator for the  3-phase alternator (not as much choice 20+years ago) and Honda switchgear and is very happy running negative earth. Even the 22 year old Boyer just works as intended.

.. with George - as time rolls on and I become less observant I like all my bikes and cars to have the same polarity. Negative earth seems to make more sense for some reason (yes I know it's illogical and the electrons go the other way anyway).

On the bikes I have 6 has positive earth, 4 has negative earth and 1 has only a magneto. Have no problem with that. On half of them, I want to keep them mostly original. Latest bike I rewired got positive earth. Simple reason was that I got a cleaner wiring with a red wires inline fuse from battery to earth.