Commando negative earth conversion

I honestly would not bother, the hassle of convertion would far outwiegh any advantages you may gain.

As for fitting equipment designed for neg earth this should be fairly easy to addapt if you ensure both the feed and return wires of any equipmentare insulated, then you should be able to connect pos to pos and neg to neg with no problems. This should also apply to LED bulbs too, just ensure the bulb holder is not directly earthed as on the pilot light / instrument lights, then just simply ensure the centre feed positive is connected to the earth and the return negative to the negative feed wire.

On the subject of LED bulbs, if you go onto Paul Goffs Website you will find he sells Instrument panel bulbs designed for pos earth as well as neg earth so the standard bulb holders can be used without the need to insulate them.

Hope this has been of help.

Paul Goring.

Totally agree with the above message. It is possible to convert the system to negative earth but.................If you make a mistake it could prove to be a very expensive one. Some Power Boxes have a reputation for dying, all too easily, if the system wiring is not sorted 100%. I recommend that you talk to both Al Osborn at AO Services and Paul Goff. Both have knowledge, experience and the right bits on sale to save you from DIY electrical suicide.

Phil Hannam

Hi, I successfully converted my Mk111 to negative earth a few years ago. It was straightforward and I have had absolutely no problems whatsoever with the bike since. If you take your time, don`t rush it and do one part at a time all will be well - no guarantees of course, but it worked for me!

A good idea would be to take photos of the individual wiring connections and/or do drawings of same as you go, then you can refer back to these if you get stuck en route. Also refer to the original wiring in the workshop manual. (Factory or Haynes)

Those nice people at Boyer Bransden may well send you a wiring diagram showing positive AND negative connections for the Boyer Mk111 unit, ignition coils (standard) and the Boyer Powerbox too. I know this `cos they sent`em to me when I asked them!

Any way, if you would like details I`m happy to post them on the forum, it`s a bit lengthy in content so I`ll dig out the info if you want, let me know on the forum.

Chris Grimmett previously wrote:

I have converted to negative earth but I was rewiring the bike from scratch and not using the usual wiring loom. My advice would be to stick with positive earth unless you are doing the total rewire; going ahead with reversed colour codes feels like a recipe for disaster sooner or later and could lead to a scenario as depicted on page 17 of Rh269. If you do rewire, I would recommend installing real earthcable rather than the horrid practice of using the chassis (just my opinion).

There is an earth wire in the loom-yes it is the wrong colour, but no need to add a 'real earth' Yes might be best practice to rewire to get it right, but it should work with some care.

Dave Evans previously wrote:

Has anybody got any ideas about converting the Commando to negative earth? I have recently bought a HID headlight and the wiring for it is obviously designed for -ve earth. I'm running a three phase alternator, Boyer power box and Boyer Mk3 ignition.

I plan to connect the battery the other way round (ie use the red wire that is currently earth, and pretend it's black, and call the black wire red and supply the systems with it) and ensure that the power from the Power box is correct to the battery and the supply to the Boyer ignition box is correct. the only other glitch will be the ammeter working in reverse, (easily swapped over)

I realise it goes against the grain to connect the black to positive and red to negative but the red wire is screwed to the frame in all the right places and would make a good negative earth.

Any body see a snag with my theory? it also means that commonly available LED bulbs could be used.

Dave Evans