Changing Commando from +ve to -ve earth

You say your none mk3 bike has an electric start system fitted. If this is the Alton Ekit type it only works with positive earth systems as it is intended to be fitted to a standard Commando. I believe that if you reverse the polarity of the supply the starter will spin in the wrong direction.

Smiths Electronic Clocks can be fitted +ve or -ve earth.

You only give us the basics to work on. Boyer electronic ignition can be wired to run with neg earth, the diagram is supplied with it. Boyer Power box the same. If you have an Alton electric start, then without looking at their diagram, provided that the fat wires to the starter remain the same way round relative to the battery, the only issue is that the power through the starter solenoid will be in a different direction but it should still hack the solenoid.

The issue with the Alton Ekit is the direction of rotation of the motor. It states in the instructions for mine that it is for positive earth electric system and the instructions make no mention of being suitable for negative earth use in fact no mention of negative earth or the consequences of installing it that way.

I think contacting Alton direct an getting an answer from them is the only prudent way to proceed with this. These kits are not cheap and i for one would not like to take chance of damaging it even though I have modified it for RGM belt drive and Maney outrigger bearing.

I have a capillary type Smith oil pressure gauge fitted as all the electrical type are designed for negative earth and due to the Ekit i didn't want to reverse the polarity of the supply. I also have LED lights fitted and as already stated Smiths electronic clocks work with negative earth so why change? What are you looking to fit Jim ?