Lucas/Wassell 1970-74 Norton Commando Main Harness

Grant Tiller

Wassell make a great wiring loom for the Norton Commando.

Specifically I am referring to Lucas Part Number 54960723 which is listed as being for the 1970-74 Commando.

Wassell sell this item under the Lucas name, as they have licensed the rights to use the name for some of the classic motorcycle parts.

An excerpt from the Wassell website about this licensing deal is as follows:

In 2014, Wassell acquired the licence for the Lucas brand from Lucas Industries Limited, for Classic Motorcycle parts. In conjunction with Lucas, an extensive product development programme for Classic Motorcycle parts was initiated, to once again, establish Lucas as a market leader within the industry. Further information is available at

In 2019, Wassell acquired the extended licence for Lucas Classic products, and Girling products worldwide, for Classic motorcycles. The Lucas Classic programme launched in 2019, and included the Lucas Classic Car, Lucas Classic Landrover, and Lucas Classic Motorcycle divisions.

The Wassell history page is an interesting read, and I urge you to take a look!

Grant Tiller

However, since the very beginning, the “Installation Plan” on their website which is also handily printed in colour and included in the packaging when you buy the item is actually wrong.

A special thanks goes to our Norton Commando community friend Constant Trossèl from Holland Norton Works for pointing out the incorrect wire colour on the Master Switch – I missed that one!

Grant Tiller

Here is the original “Installation Plan”

Grant Tiller

I have highlighted the parts that are incorrectly labelled and wrongly drawn – particulalry annoying is that they could not get the Lucas part number correct on their own drawing:

Grant Tiller

This is the corrected version of the “Installation Plan”

Grant Tiller

I have contacted Wassell about this a couple of times in the past, as I have helped a few people that have run in to issues.

However, it has fallen on deaf ears, and several years on they still have not changed it.

Hopefully this will help someone somewhere!!!!

There are several errors on the paper instructions/guides that come with the Lucas/Wassell harnesses.

To my knowledge, the harnesses themselves are fine – they are made by Autosparks, whose history can be traced back to the original ones supplied to Norton.

Here are the pages with corrections:

17 replies

  1. I purchased the exact wiring harness, laid it out on the bench and got out the masking tape and proceeded to tag the terms, yes, I immediately spotted the two mistakes you have shown. Thanks so much for all you do Grant!

  2. Hi Grant,
    Much obliged for your valuable information on this matter.
    I have just purchased this wiring harness for my ’74 and am VERY GRATEFUL for the information.

    Cheers Don from Oz

    • It’s great to hear it helped someone Don!

      Nearly ten years on, despite a number of people telling them, they are still sending out the harnesses with the wrong picture!!!

      Thanks and take care,

  3. Hi Grant,

    I am fitting the Lucas Main Harness to my ’74 Roadster frame.

    Upon testing the earthing system (all red wires back to the red battery eyelet) I came across 4 wires (that were marked as errors in the original diagram that came with the main harness by you). These wires are 3 x red wires and the horn wire. Two of the red wires go into a double connector from the same direction with no wires exiting the other end. These two wires test full deflection on my analogue ohm metre to the red eyelet at the battery end. Then there is the single purple/blue wire that comes from the horn. The 3rd red wire just has a bullet terminal on its end and it does not test full deflection on the metre at all. No movement on needle – does this mean this red wire is open circuit somewhere which I need to chase out or am i missing something else with this wire.

    On your corrected version of the 70-74 Main Harness you show a loop on an earth wire that comes out with the horn wire. So should this red wire with bullet terminal be looped around and back into the double connector?

    Also on your corrected version of the main harness on the bottom side of the main sheathing/wiring there are two large black dots on the end of two earth wires – does this indicate anything of significance (like connect to frame or other place)?

    Thanks again Grant for any advice and help you can offer me.

    Don Clifton

    • Hi Don,

      Yes, there are a bundle of the red cables at the horn.
      The two is the loop in and out for the positive red feed that runs from front to back of the bike.
      The single, if memory serves me right is the positive red feed that goes off to the power socket.
      So when it is unplugged, you should see full continuity both ends (horn end, and power socket end) but no continuity to the rest of the reds on the harness.
      Plugging it in, as I have shown clearly on the amended diagram will liven up the power socket and give you full continuity with every other red cable in the harness.
      This will leave you with one spare port on the connector for the positive feed to the horn.

      The other single cable you should there is a PB (purple and black) cable.
      This should come out at the big bundle of cables under the tank, and is where you plug in the purple and black from the horn push on the handlebar switch.
      You should see full continuity between both ends of the purple and black ends.

      Lucas (Wassell) show ring terminals as the big black dots.
      So the bottom left one is at the head steady, and the other is at the zener diode (they quite rightly do not depend on getting a positive feed from the frame)

      Hope that helps.

  4. Hi Grant,

    Thanks so much for the valuable info. I understand a bit more now.

    More testing to be done with the ohm meter tomorrow.

    Cheers Don

  5. Hi Grant,
    I am in need of some help with trouble shooting.
    I have completed fitting the new Wassell main and headlight harnesses to my ’74 Roadster.
    The issue is that with the ign “on” when the indicator switch is operated the plugs spark which are laying on the cyl head.
    I have thoroughly tested the indicator switch wiring to ground (i.e. alloy housing) and between each of the wires with an ohm metre and visually inspected the wires in the switch – all okay.
    I have a Boyer fitted (blue box) and Pazon dual coil. The Boyer red wire goes from blue box to + on the coil and then to ground. If I use the ground that is under the tank to the Boyer the spark plugs will spark when the indicator switch is operated. If I move the Boyer red wire via a jumper lead to the + battery terminal or the 4-way ground connector at the rear of the air cleaner then there is no sparking at the plugs.
    I have checked the ground wires from end to end and get a zero reading. So for all intents and purposes it looks like the wires are in good condition and not damaged at all. But who knows what lies under that woven sheath covering.
    Thanks Grant
    Regards Don

    • Hi Don,

      Remember the blue box Boyer is digital, and requires special coil(s)

      Yes, the Boyer red cable and the coil positive feed should both meet at the red cable that goes into the harness at the head steady.

      It is important to make sure this is at the head side of the head steady, not the frame side, as it will impact the quality of your spark!

      Your issue doesn’t sound like a positive earth problem though – more like a negative supply.
      The fact it is not behaving as it should, and with the turn signals in the mix says to me there is a white cable not in the right place, or the ignition switch itself is not wired correctly.

      Do make sure you check that ignition switch, the order of pins looking at the bottom is 1, 4, 2, 3 where pin 2 has the two white cables attached – one to the flasher unit, and the other into the harness toward the front of the bike.

      There is a diagram of the switch and how it is wired here:

      Has the ignition switch been replaced, and is it the correct one LU30552
      The Triumph one LU35351 is easier to get hold of, and sold by more shops, but while it looks similar, it is different, so watch out for that!

  6. Hi Grant,

    I am using a PAZON Dual Output Digital Ignition Coil with the Blue Box Boyer.

    I have modified the earth wire that usually attaches at the nut of the head steady stud. I have extended the wire and it is attached to the bolt that holds the head steady to the cyl head. So a direct good engine earth with the stainless cap screw that screws right into the top of the cyl head.

    I do have a concern that I do not have a decent earth to the frame. As I am not using a zener diode that means that I have not fitted the zener earth to the “Z” plate. Also there is no provision inside the headlight shell for an earth there. The old shell had a small round fitting that was rivetted to the inside of the shell that an earth wire would push into. So I’m not sure how the indicators get there earth in my case.

    I have checked the ign (master) switch and it is the correct 4-terminal type purchased by me from Andover. The wires are all attached to the correct terminals and all the connections under the tank between the main harness, the headlight harness and the two grey cables running to the two handlebar switches are correct as I recorded this information before disassembling the old harnesses.

    I did more testing today. When I removed the rear indicator bulbs and ran the test the plugs did not spark. I then refitted the rear bulbs and removed the front bulbs and redid the test. Again there was no sparking at the plugs. But when I had all four 21w indicator bulbs fitted the sparking of the plugs was present again.

    I ran individual external jumper wires from the metal bulb holders in each of the indicators to see if a good earth from bulb holder to “+” side of battery would improve things but unfortunatel the plugs continued to spark with ign on and indicator switch in L or R position.

    One other test I did was the remove both of the wires going from the blue box down to the points housing in the timing chest and repeating the test again and the plugs continued to spark!!!!!!!

    Grant I’m afraid that is all I can tell you.

    Cheers Don

    • Hi Don,

      As I say, I don’t personally believe your issue is earth related at all.
      And don’t be concerned about earthing to the frame – the Norton Commando was designed to have no reliance on the frame for positive feed – there is a red cable that runs along the harness to feed the good stuff to all the important bits.
      There are a couple of gotchas which are covered in this article here:

      I think the next thing for you to do is to isolate the ignition from the rest of the bike, and determine if it is a wiring problem or a component problem.

      Start by temporarily running a cable from the battery negative terminal directly to the Boyer white cable, and see if the bike starts and there is no other interference from other components (like the turn signals).
      This is quick and easy to do, and will help you eliminate half the issues it could be in one go.

      If the bike starts and runs fine, you are ruling out bad plugs/leads, bad coils, bad timing and carburation issues but most importantly anything to do with earthing.

      Assuming that all good, and there are no issues, reconnect the Boyer white cable to the W/Y (white/yellow) cable from the kill switch and this time disconnect the white cable that goes to your flasher unit.
      Do the same checks again does the bike run okay, and does everything on the bike (apart from the flashers) do as you expect.
      Additionally check the engine stops when you turn off the ignition key switch, and that the engine stops when you press the handlebar kill switch.

      Hopefully these two quick and simple checks will allow you to pinpoint your issue!


  7. Hi Grant,

    I could not follow your advice as the bike is in the final throws of restoration which has taken over 6 years. Therefore I could not start it.

    Anyway the problem has been fixed.

    I located the zener diode wires and insulated the end of the live spade wire and attached the earth ring terminal onto the rear of the “Z” plate. I refitted the 4 x indicator bulbs and did the test which involved turning the ign on and operating the indicator switch and to my great joy the spark plugs did not spark. I ran the test a few times which included operating the paddle switch in the up and down positions and was not able to produce any sparking of the plugs from the Boyer unit.

    Many thanks for the time you took to communicate with me on this.

    Regards Don

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