Custom Norton MK3 Commando Wiring Diagram (Graham Tiller)

Grant Tiller

This is a custom wiring diagram for Graham Tiller – MY DAD 🙂

Electronic Ignition

We have fitted a Tri-Spark electronic ignition to his bike.

Grant Tiller

3 phase Alternator

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

Grant Tiller


We also fitted the superb Shindengen SH775 regulator/rectifier – it’s the only way i’d ever dream of fitting a lithium-based battery to a bike.

Grant Tiller


Talking of batteries, we went large!

We fitted a Shorai LFX36L3-BS12 (note this is a pre-MK3 battery tray, so the battery runs along the bike, not across it)

It is 36 Ah (or the lead acid equivalent) – but more importantly it has 540CCA (cold cranking amps)

It turns the engine over like the plugs aren’t in it!

Grant Tiller


We also fitted Colorado Norton Works handlebar switches (modified Honda units) because we fitted a Brembo brake master cylinder and ‘matching’ Magura clutch lever so were no longer bound to the original switchgear.

Grant Tiller
Grant Tiller


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

Grant Tiller

Charge Warning Light

The final thing worth noting is the Charge Warning Light.

Grant Tiller

The nice thing about the Improving Classic Motorcycles unit is that you can retain the original warning light – so it looks totally factory.

It gives you a lot more useful information about the state of the battery and charging system compared to the standard assimilator unit, which looks for AC output from the alternator stator only.

Grant Tiller

Here’s the bike basking in the sunshine!

Grant Tiller

Wiring Diagram

Here is the Wiring Diagram for Graham’s bike.

Custom Norton MK3 Commando Wiring Diagram – Graham Tiller PNG 3066×1841

Grant Tiller

14 replies

    • I see charge voltage top out at 14.8 volts DC with the Shindengen.
      At very low RPMs, the lowest I have seen is 14.5 volts.

      Personally I would prefer to see the peak voltage set a little lower than it is on the SH775 – but it was not designed specifically for lithium-based batteries, and this really is the best I have found so far.

      • Grant, actually, for a LiFe battery, those are great charging voltages. While a lead acid battery is considered fully charged with a resting voltage between 12.8 volts and 13.2 volts [ideal], LiFe batteries take more voltage. I would suggest you visit Shorai’s FAQ page, linked below.

        Open the “Can I Use Lead-Acid Battery Chargers or Charger/Tenders? question. View the battery charge level chart.

        • Yes, I have an ok understanding of battery chemistry.

          The absolute peak charge voltage for a LiFEPO4 cell is 4.2 volts per cell (so 16.8 volts for an automotive battery)
          At that point, the cells start to become damaged and life of the battery is degraded.

          In my opinion, I would only want to charge at anything approaching an upper rate on a per cell basis, and on the grounds that no regulator/rectifier interfaces with a charge balance port on the battery itself addressing charge rate on a per cell basis (like the manufacturers dedicated chargers do)
          For me, personally, I am much more comfortable sticking with the lower charge rate as far as what the reg/rec puts out.

          There are some exceptions to this – batteries like the EarthX ones that contain a charge circuit built into the battery casing itself that will address the individual cell requirements and make sure that charging is balanced.
          These are superb batteries, but you pay for the privilege, and I would suggest these are not the off the shelf batteries people are buying to put in their bikes.

          – EarthX specify 14.6 volts as the absolute maximum charging voltage, even with their clever BMS circuitry (battery management system)
          – Shorai is 14.6 volts
          – Antigravity is 14.7 volts
          – Ballistic is 14.4 volts
          – Skyrich is 15 volts
          – Shido is 15 volts (they have a built in BMS)
          – Western Power Fire Power Featherweight is 15 volts

          Personally, I would feel most comfortable if the charge voltage threshold was capped at 13.8 volts when Lithium-based batteries are concerned.

          …I am still searching for that perfect series-type MOSFET reg/rec that charges at 13.8 volts. But haven’t found one yet!

  1. The Shorei battery you are using would never fit in a Mk III battery tray/air box configuration. You should have mentioned that you replaced the stock battery tray with an earlier 750/850 battery tray. I like the chrome battery tray! Without a LiFe battery, that would be cosmetic suicide [leaking acid] Thanks for your great web site.

    • This site tends to focus on the electrical side, so I haven’t gone into any detail on any of the other stuff we’ve done.

      The MK3 has been subtly modified quite a bit in addition to the electrical changes:
      – Corbin seat
      – moved front brake from left front to right back
      – 18” rear wheel
      – pre-MK3 ham can air filter
      – pre-MK3 stainless steel battery tray
      – stainless braided lines
      – 13mm brake master cylinder
      – drilled discs (not shown in the picture)

      I’m glad you like the site – hopefully there is something here of use to you!

  2. Hi Grant,

    What a fantastic concept in the open type regulator SH775. I’m located in Australia and I have managed to purchase from the USA 2 of the original SH775 Rectifier/Regulator. Can you provide me with a description of the connector type that is required to interface the SH775?. Also is it possible to give me the pin outs of the SH775, from the photo of your installation of the SH775 I can clearly see the positive and negative DC outputs.

    • Hi Leigh,

      The Shindengen SH775 is by far my preference, I have never had one go wrong (nor have I heard of any failures).

      Plus, from a technical standpoint, I like the way they open the circuit when charge is not requred – it just makes sense to me.

      Here is some info around the pinout:

      pin out

      On the bike, it is wired like any other reg/rec:


      The connectors are very common on Yamaha, Kawasaki and Honda bikes (and modern Triumphs)

      They usually go by their trade name of Furukawa Connectors

      An example can be found here:

      However, the spade types are 6mm in size, so I often see them wired with standard Lucar type spade connectors, as it means a lot less bulk from a size perspective.


      Hope that helps!



  3. Good afternoon Grant,

    Thank you so much for the rapid response it is greatly appreciated. You have answered all of my questions in great detail, thus allowing me to progress this project. PS It’s great to see such a comprehensive web site dedicated to Classic Motorcycle Electrics.


    Leigh Roberts.

    • Yes, the Honda part numbers are as follows:

      35200-MY6-A91 for the turn signal/lights/horn switch
      35130-MY6-A91 for the engine start and run/kill switch

      They were used across several models from the early 2000s onwards including the XR650

  4. How can I get a wiring diagram for the Honda switches. Your information is well documented and any heads up would be appreciated.

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