Custom Norton Commando Wiring Diagram – Richard Dodds

Grant Tiller

Richard Dodds has a Canadian Spec MK3 Commando, but has made some modifications to it inline with modern motoring and reliability.


First up, Richard has fitted a Tri-Spark electronic ignition to his bike – this is a great pairing for a MK3, as the circuitry really minimises kickbacks, so it is much kinder on that delicate sprag clutch!

You can find the Tri-Spark website here.

Grant Tiller

The Tri-Spark unit is a one box solution – all the gubbins are mounted inside the points cover – no additional black box to try and hide under the tank, and very very simple to connect up.

The wiring is as follows:

  • Red wire – this is the positive feed to the Tri-Spark unit. Most people attach this wire to one of the two fixing posts inside the points cover. I would personally recommend running an additional wire up to the coils and have drawn it this way on the wiring diagram.
  • Black/Yellow – this is the negative feed to the Tri-Spark unit. This joins in to the White/Yellow that is the kill switch on your right side handlebar switch (the Ballast resistor is no longer required)
  • Black/White – this is the negative supply FROM the Tri-Spark TO the coil.

You’ll note in the wiring diagrams below that the Ballast Resistor and Condensers have been removed as part of the conversion to Electronic Ignition.

Two major benefits of the Tri-Spark:

  1. a very low operating voltage – as low as 8 volts means your bike will still run with a less than optimal battery and charging system
  2. circuitry performs the electronic equivalent of advance and retard to make the bike easier to start and stop the possibility of kick-back. This makes it gentler on your knees, and kinder to electric start systems (aka the delicate Commando sprag clutch)


In lieu of the twin 6 volt coils, Richard has fitted the dual output single tower coil from Colorado Norton Works (it’s the brilliant Crane Cams unit) and looks much neater.

Grant Tiller


He has also fitted a 3 phase Lucas alternator – a nice choice for superior charging in modern traffic conditions.

Grant Tiller


To go with the three phase Stator, Richard has fitted a Podtronics 3 phase regulator/rectifier in lieu of the half wave rectifier and twin zener diodes of the MK3.

This will bring the voltage up a little too!

Grant Tiller

Battery Status

Grant Tiller

Richard has fitted a SparkBright voltage monitor instead of running with the standard warning light assimilator.

Wiring Diagram

Custom Norton Commando Wiring Diagram – Richard Dodds PNG 3066×1841

Grant Tiller

5 replies

  1. Again, many thanks for doing the custom wiring diagram for me, have just laminated an A3 copy for my workshop wall.
    I’m afraid i’m not too clever with electronic stuff, so was hoping you could please advise me:-

    Deutsch connectors

    DT type is slightly bigger, has size #16 terminals and 2 wire sizes, 14 – 16 (with green bands on terminals,) 16 – 20 (plain terminals) . Rated at 15amps.

    DTM type is smaller, but also has a moulding each end for shrink wrap, which makes it longer. Only size #20 available. Rated at 7.5 amps.

    My new loom is made up with 20 awg size wire.
    As I already have a few DT type plugs I will use them and use the shrink wrap that has glue inside.
    I guess the wire to the headlight draws the most power? Just wondering what the typical amps through these wires is?
    I have the standard glass 35 amp fuse fitted, but would like to change to modern car type, but believe the 2 types are rated differently?
    Would appreciate very much any advice you can give
    Kind regards

    • For speccing out your connectors, take the worst case scenario:
      A quartz halogen main beam at 60 watts.
      You have a fully charged battery at 12.6 volts.
      …that means you are drawing 4.7 amps.

      In reality:
      A typical H4 dipped beam is 55 watts.
      Your Podtronics is putting out 14.6 volts.
      …that means you are drawing 3.8 amps.

      I use the smaller DTM connectors – that are rated at 7.5 amps in continuous use everywhere apart from the alternator wires – where I use the DT connectors which are rated at 13 amps.
      I use the nickel-plated solid connector pins, not the stamped ones.

      Check out the Deutsch Jiffy Splice – it is a connector that accommodates a single pin and socket and takes up very little space.

      The size 16 Jiffy Splice holds the DT connector size pins.

      Do bear in mind the difference between the US and UK way that fuses are rated:

      The British Standard used rated fuses by the current that would make them blow instantly.
      The American (and now international) Standard rates fuses by the amount of current they will carry forever.

      With larger fuses, it becomes an issue and you stand a chance of melting your wiring.

      For example, a Norton Commando factory workshop manual (written for the Brits with the British Standard in mind) specifies a 35 amp fuse.

      A 35 amp North American fuse is around double the rating of what a 35 amp British fuse would have been back in the day.

      And at this point, all the insulation would be melting off your wires before the fuse blows.

      The equivalent automotive blade fuse would be 17.5 amps but that value is not readily available – as a rule of thumb, I upsize to 20 amps for a MK3 and downsize to 15 amps on a pre-MK3 as these are standard values and are sold at every petrol station

      Always bear this difference in mind when reading the manuals, and replacing the fuses.

      How fuses are rated now makes no difference to the way the manuals are worded in the books we’ve all got on our shelves.
      If I bought a glass fuse from my local autostore today, it would be a 20 amp fuse, even though my manual calls for a 35 amp fuse.

      Also consider wire sizes, and remember that your fuse must always be the weakest link!
      The typical wire sizes used by Lucas that we see on our classic bikes, are rated as follows:

      44 strand
      44/0.12 (44/0.30mm) 22 amp

      28 strand
      28/0.12 (28/0.30mm) 14 amp

      14 strand
      14/0.10 (14/0.25mm) 6 amp
      14/0.12 (14/0.30mm) 7 amp

      9 strand
      9/0.12 (9/0.30mm) 4 amp

      Note 1 – the 14/0.10 was superseded by the 60s
      Note 2 – modern cables of the same spec are rated higher than the figures Lucas give (as shown here)

  2. Hi Grant,
    Thanks for all this useful information, which even I can understand. I was most interested in the Deutsch jiffy splice connectors but haven’t seen them here in New Zealand. They would be great for inside the headlight shell and getting thru the shell rubber grommet. There’s a place in Auckland that specialises in performance car electrics that sells Deutsch connectors, about 4hrs from here. Will pay them a visit. Just wondering what brand of crimping tool you use? The one’s I have seen here are very expensive, over $100 and only does one size terminal. I am currently also thinking of getting a Tri Spark mofset regulator, to keep as a spare incase the Podtronics one fails.
    Kind regards

    • I try to steer clear of universal crimping tools.
      For the Deutsch connectors I use this one – it only does Deutsch connectors:

      It is the HDT-48-00 made by TE (who make the connectors)

      It is spendy for sure, but I have done hundreds of connectors, and it is still as good as new and will probably outlast me!
      Link here

      I get a lot of my stuff from these guys – they are in the US, so I don’t know what shipping costs to New Zealand would be like:
      Worth looking at their website, even if it’s just for ideas of all the different connector types and sizes that are available.

      The new Tri-Spark reg/rec is a big step forwards.
      MOSFET instead of the old Thyristor based SCR technology means that voltage control is far more accurate.
      Still a little higher than I am happy with if you are considering lithium-based batteries.
      The downside for me is that, like the Podtronics (and many of the other reg/recs on the market) they are still short-type.
      That is to say, they dead short the alternator stator windings when no charge to the battery is needed.

      I don’t like this idea, and out of principle, will not install these on my bikes.
      I feel it is no coincidence that the number of charging issues have gone through the roof since the introduction of the reg/rec, compared to the last 40 years when everyone’s bikes have been totally fine.

      The only reg/rec type I like is the series-type.
      These open the AC circuit when charge is not required, taking the load off the alternator stator windings completely.
      I am looking all the time, but at the moment I still feel the Shindengen SH775 is the best available for our bikes.
      There is a great article on this site by Jean Des Rosiers which covers the Podtronics ‘vs’ the Shindengen

      Hope that helps.

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