Norton Commando Wiring Diagram + Alton Electric Start Kit

Grant Tiller

Alton Electric Start kit

Grant Tiller

These are superb quality, well-engineered and made in France.

They allow you to keep the triplex primary chain and the factory standard ‘ham can’ air filter.

They come with their own bespoke alternator stator and rotor as part of the kit.

And while it is ‘only’ single phase, and can quite easily work with the original zener diode-based charging system, it is worth noting that Alton recommend that you fit a PODtronics combined regulator/rectifier instead.

The Alton alternator puts out around 90 watts at ‘cruising speed’ which is plenty – it is more-or-less the equivalent of the original RM21.

Grant Tiller

Battery Connection

As you read through this article, and start to look at the diagrams, be sure to notice that there is only one connection to the battery positive – this is the heavy 6-gauge cable that goes to the primary case for the Alton Electric start.

It is important not to take any other connection to the battery on this side, as if for any reason you have disconnected the heavy gauge cable (maybe you are doing some maintenance work on the primary), and you inadvertently touch the starter button, you can quite easily pull 200 amps of unfused power through the other cables in the wiring harness that are rated at 20 amps.

The wires simply melt!

NVT had the same problem with the Triumph T160 back in the day.

They sent a Service Bulletin out to the dealers and distributors instructing them to cut the light gauge wire from the battery, leaving only the heavy one. The same thing should be done on the MK3 Commando too (there are a lot of commonalities with the electrical system on the MK3 Commando and the T160 Triumph, as they were under the same ownership by that point)

All of the MK3 diagrams here on my site have that cable deleted for this very reason.

Grant Tiller

You often see MK3’s with this cable cut. I think it is common for a new owner of a bike to wrongly reinstate this wire when they open the side cover for the first time and discover that the wire has been cut. Wrong – it’s been cut for a very good reason!!!

Install Guide

The Alton kit comes with a very well written installation guide, which you can access here:

Grant Tiller


There are lots of circuit diagrams in the installation guide, which hand hold you through adding the Electric Starter kit to your bike – this is really helpful and shows superb attention to detail from the Alton guys – so kudos to them!

Grant Tiller

Another point worthy of mention is the positive feed from the battery – I mentioned it before, and I’ll say it again – there should be one heavy gauge cable from the battery positive to the back of the Alton primary case and nothing else.

The harness (i.e., the rest of the bike) receives it’s positive feed from the ring terminal on the engine side of the head steady.

The Alton diagrams suggest that the battery should have an additional lighter gauge positive feed. This is not correct.

Grant Tiller


Alton advise in their instruction manual that you should uprate the battery.

I have had good experience with Motobatt and would certainly be pleased to recommend the MBTX20UHD

Grant Tiller

This is a great choice – I really like the Motobatt AGM batteries, they seem to get through a winter layup with no problems at all.

No need to leave these on a tender over the winter, just a charge the night before your first springtime ride of the year, and you are good to go!

AGM is a sealed battery, so no worries about venting or spillage.

They are not overly expensive, and their Cold Cranking ability is good, making them a nice upgrade for electric start bikes!

Wiring Diagram

1971 (three wires to the master switch) PNG 3066×1841

This is available as a PDF too – it can be downloaded here.

Grant Tiller

1972 onwards (four wires to the master switch) PNG 3066×1841

This is available as a PDF too – it can be downloaded here.

Grant Tiller


A couple of points about the way these diagrams have been drawn:

  1. Where the same colour wire goes in to and out of a single connector, that connector has usually been omitted from the drawing.
    It’s obvious on the bike, is easy to spot and easy to troubleshoot.
    Leaving them off the diagrams makes them a LOT easier to read, and considerably less cluttered.
  2. Wherever the earth or ground side of a component goes back to the battery, the drawing shows a red earth symbol:
    Grant Tiller
    In reality, this could be connected either to a red wire in the bike’s wiring harness (loom) OR it could be attached to the frame or engine of the bike.

    I have shown the red earth symbol each time in order to massively simplify the diagram, and make it a lot easier to understand for everyone.

    I have also coloured them red as a gentle reminder that these bikes are wired positive earth!

2 replies

  1. Hi, Grant.
    Great website and very useful. I am just rewiring a Norton Commando interstate 1972 and i have been using your guide, the machine has an Alton electric start and a Boyer ignition system. You state that only one wire to be connected to the positive terminal to the primary case , just wondering what people do with the red wire from the loom that used to connect there?
    Do i cut the ring connector off and tape it up leaving the red wires still connected to each other?

    • Hi Mark,

      Simply disconnect the ring terminal from the battery and tape it up with some insulation tape.

      It is important that the red cables are connected to each other for continuity of the positive feed from front to back of the bike.


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