This page covers two aftermarket upgrades seen on our Norton Commandos.
- Tri-Spark electronic ignition.
- Tri-Spark MOSFET regulator/rectifier.
Electronic Ignition
The new kid on the block for Electronic Ignitions is Tri-Spark.
Well, I say new kid – they have been around since about 2009.
You can find the Tri-Spark website here.
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:
| Wire Colour | Description |
|---|---|
| Red | 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 the wiring diagrams accordingly. |
| Black/Yellow | This is the negative feed to the Tri-Spark unit. This joins in to the White/Blue wire that used to feed the Ballast Resistor that you are removing. As standard, this goes up to the big connector block under the tank, where it’s joined to the White/Yellow that is the kill switch on your left side handlebar switch cluster. |
| Black/White | This is the negative supply FROM the Tri-Spark TO the coils. |
From a wiring perspective, the most important thing to note is that you will be moving from a pair of coils that are wired in parallel to series.
Originally, the points make and break the positive (earth) side of each coil in turn.
The Tri-Spark electronic ignition system uses a concept called “wasted spark” – with the two coils wired in series, they are energized together on every rotation of the camshaft.
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:
- 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
- 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)
Regulator/Rectifier
Matt used to recommend PODtronics, but switched to the Tri-Spark MOSFET reg/rec.
It is relatively new to market and more details can be found here Tri-Spark MOSFET
It is certainly easy to spot in it’s blue anodised heatsink!
There are five wires to connect:
| Wire Colour | Description |
|---|---|
| Yellow (x 3) | these are the AC input and pick up on the three wires coming out of the three phase alternator stator (connection can be any way round, as this is the AC side of the circuit) |
| Red | this is the Positive output and will join to one of the red wires in the harness |
| Black | this is the Negative output (known as the hot wire) – it will be wired to the NU (brown/blue) that goes back to the battery negative terminal via a fuse |
The spec on paper is very good, being able to handle up to 20 amps.
And the benefit of MOSFET is much more precise control of the charge voltage. I have done a deep dive into reg/rec types and behaviour which you can find here
Here are the wiring instructions for the Tri-Spark VR-0030 MOSFET regulator/rectifier.
Alternator
A three phase stator is a great option to go for and is far superior to the factory original single phase unit.
The spec for a pre-MK3 would be as follows:
- Lucas RM24
- 3 Phase
- 10.5 amp
- Part Number LU47252
- Also found under Part Number WW10193L
For a MK3, you would typically spend most of a ride recharging a heavily depleted battery due to the power hungry starter motor.
Therefore, you can consider the higher power stator:
- Lucas RM24
- 3 Phase
- 14.5 amp
- Part Number LU47244
- Also found under Part Number WW10192L
With a three-phase unit, output is produced at a much lower RPM making this an ideal solution for around town and in stop start traffic conditions.
As always, we recommend that you ride with your headlight on, as this will always help with the longevity of the components that make up your charging system.
Warning Light Assimilator
The factory warning light assimilator is not compatible with most modern regulator/rectifiers and the Tri-Spark MOSFET reg/rec is no exception so it has been removed from the schematics.
Plus, there is the matter of what the WLA is actually doing, and how much use that is.
The WLA is looking purely for some AC output from the alternator stator (about 6 ½ volts AC) it is not designed for a three phase stator either.
It gives you no information about the charging (i.e., the regulator (zeners) and rectifier)
It gives you no information about the state of the battery.
Charge Warning Light
I have taken the liberty of adding an ICM Charge Warning Light to the schematics – I can certainly recommend the Improving Classic Motorcycles charge warning light as a brilliant alternative.
I use them myself, and have had a good experience with them.
The nice thing about the Improving Classic Motorcycles unit is that you can retain the original warning light – so it looks totally factory (this for me is an important factor with the MK3 with it’s quirky little instrument panel).
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.
1968 Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
These are the pre-1971 bikes and have the ammeter in the headlight shell, as well as the Wipac Triconsul type handlebar switch.
The wiring is very simple, and more like the Atlas than what came to be familiar with the Commando.
Note that I have included the Front Brake Switch as standard – this was a US requirement, that didn’t appear on the earliest UK bikes.
1968 Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1971 Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
This is often referred to as the “Interim” model.
It is distinguishable by the three pin master switch (ignition key switch) which was Lucas part number LU39565.
These were made ONLY for the Norton Commando, and are no available as an aftermarket replacement.
If you are not comfortable rebuilding the switch, most people choose to go for the LU30552, which IS readily available.
You can find an article on ignition switches here, that may be of interest.
1971 Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1972 onwards Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
The 1972 onwards schematic covers 750 and 850 bikes and has the much more familiar four pin master switch (ignition key switch)
1972 onwards Norton Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
MK3 Commando
During the manufacture of the MK3, Norton and Triumph were coming together, and they were often feeding from the same parts bins.
We have noted some anomalies between the handlebar switches while the MK3 was in production, as they frequently used the Triumph T140E switches, which look the same, but have a couple of small wiring differences.
Left handlebar switch the U (blue) used by Norton (and illustrated in the factory workshop manual) has been replaced with a UY (blue/yellow) cable. This connects to the U (blue) of the right handlebar switch inside the headlamp bucket.
Right handlebar switch there is no S (slate grey) instead, the single “hot” negative from the pin 2 of the Master Switch (ignition key switch) is jumpered for both engine run/kill switch and the starter button.
Another element of the MK3 that sometimes causes confusion is the wiring around the Warning lights.
The factory workshop manual shows the following:
I have covered this in more detail in a separate article, which can be found here.
But in short, the cable colors used for the sub-console wiring harness were not the same all the way through MK3 production – so certainly something to watch out for!
1974 Norton MK3 Commando (Early) Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
1974 MK3 Early Bikes – there were around 2,000 bikes that were built around the December 1974 timeframe that have three additional fuses that can be found in the headlamp bucket.
1974 Norton MK3 Commando (Early) Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1975 Norton MK3 Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
This is the most common configuration, and takes us through to the final Commando that rolls off the production line.
1975 Norton MK3 Commando Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1975 Norton MK3 Commando (Canadian Market) Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec
For the Canadian Market, there were legal requirements around the headlamp being on while the engine was running.
A different Master Switch (ignition key switch) is fitted in order to adhere to law in Canada. More info is available here in a separate article.
This is covered in the Factory Wiring Diagram, by notes.
The Canadian key switch LU30825 is not available, and must be rebuilt manually.
1975 Norton MK3 Commando (Canadian Market) Wiring Schematic + Tri-Spark ignition AND Tri-Spark MOSFET reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
NOTE:
A couple of points about the way these diagrams have been drawn:
- The diagrams on my site are schematics – the components are not drawn in the physical location on the bike. Instead they are drawn in locations that make the diagram the easiest and most logical to follow.
- 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. - Wherever the earth or ground side of a component goes back to the battery, the drawing shows a red earth symbol:
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!
Categories: Aftermarket Upgrades, motorcycles