Richard Foster reached out via the website to enquire about a schematic that will cover his 1971 Commando.
…this one is a little different, as Richard is running a Joe Hunt magneto, and no battery.
Joe Hunt have been making motorcycle magnetos since the 1960s – and go back even further in the aviation space.
Magnetos are an attractive proposition, as they are simple and there is no reliance on a power source or charging circuit, as they generate their own power, and are self contained.
On an early Commando, the magneto sits behind the engine as per the Dominator setup.
However, on the later Commando, the points were moved to the front of the engine, and are run off the end of the camshaft.
Some people don’t like the look of a magneto hanging off the side of the engine like this, but there is no denying how effective the magneto is.
Here is the Installation Instructions for the Joe Hunt magneto
You will notice in the schematic, that the cut-out switch (or kill switch) has been wired to the unused starter button on the handlebar switch.
It is important to remember that the key switch is no longer tied to the ignition in any way at all now.
Because Richard’s bike will be running with no battery, I cannot recommend strongly enough the switch to a three phase alternator instead of the factory standard single phase one.
The 10 amp single phase RM21 provides its peak output at very high RPMs, which means at low RPMs and no battery, the headlight will at best glow instead of shine.
The other downside with a single phase alternator is that the headlight will pulse at low rpm – compared to using a three phase stator which will give a more even, more consistent light.
Switching to a three phase alternator isn’t about increased power output – in fact I would certainly recommend the low powered 10.5 RM24 stator.
It’s all about getting a decent output at low RPMs, so that around town, the headlight is still useable.
The spec is as follows:
- Lucas RM24
- 3 Phase
- 10.5 amp
- Part Number LU47252
- Also found under Part Number WW10193L
This stator has roughly the same output as the standard RM21 that came on the bike – however, the rated output is produced at a much lower RPM making this an ideal solution for around town and in stop start traffic conditions.
As always, I would recommend that you ride with your headlight on, as this will help with the longevity of the reg/rec and the stator itself.
One of the most common upgrades or modifications for a classic british bike is to add a combined regulator/rectifier unit.
Our Commandos use a blue can capacitor, zener diode (which can be found mounted on the back of the z-plate) and rectifier unit.
A combined regulator/rectifier replaces all of these components with one package.
Richard will also be dispensing with the battery, as his ignition will be run be a self-generating magento.
So I would recommend the Boyer Bransden Power Box 105
Boyer Bransden are a popular manufacturer of aftermarket regulator/rectifiers with their Power Box units which are available in single phase, three phase and high power versions.
However, one very important thing to note, which often gets overlooked is that the Boyer Bransden Power Box is not compatible with the Warning Light Assimilator used on the Norton Commando.
You can see in the note below:
Note: On Norton machines the charge warning light simulator must not be used.
Please remove it. If this feature is required please use our PBOX00106 which includes a charging light control.
While the wording is poorly put, and the grammar is bad, the message is very clear.
You can see the original instructions here:
As you can see in the instructions, Boyer Bransden sell a different Power Box unit, if you want to continue and use the red warning light to show charge. However, that is single phase only, so not suitable in this scenario.
The Instructions that come with the three phase PBOX105 Boyer Bransden Power Box regulator/rectifier that I recommend using can be found here:
There are five wires to connect:
|these are the AC inputs and pick up on the three wires on the 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 the red wire if you are using existing harness wiring|
|Black||this is the Negative output (known as the hot wire) – it will pick up on the Brown/Blue wire (which goes to pin 1 of the ignition key switch)|
General Tidy Up
I have taken this opportunity to remove the superfluous Interpol wiring, as it is of course not required on this bike.
Richard also mentioned that he is not running turn signals on this bike, so the wiring, lamps and flash unit have been removed from the schematic.
Here is the Custom Wiring Diagram for Richard’s Norton Commando with Joe Hunt magneto.
Custom Norton Commando Wiring Diagram – Richard Foster PNG 3066×1841
This is available as a PDF too – it can be downloaded here:
But wait… there’s more…
Richard mentioned that he’s building something that’s stripped down and along the street-bike and flat tracker lines.
So I have done a bit more stripping down!!!
I have replaced the headlamp for a “bates style” lamp – these are sometimes smaller in size (4 ½ or 5 ¾”) and are mounted by a single bolt at the bottom to the yoke (triple tree)
It makes for a really clean and uncluttered look.
Not only does this dispense with the headlight ‘ears’ that mount the stock headlamp to the fork stanchions which lightens up the look of the whole front end, it also does away with the three warning lights and toggle switch too (which obviously further simplifies the wiring)
I have also replaced the two lucas handlebar switches with a simple, Tricon unit, again decluttering things!
The dipswitch toggles the headlamp between dipped beam and main beam (on or off is controlled by the ignition key switch)
The black button toots the horn, and the red button cuts the engine by earthing out the Joe Hunt magneto.
Alternative Wiring Diagram
Here is an Alternative Custom Wiring Diagram for Richard’s Norton Commando with Joe Hunt magneto.
Alternative Custom Norton Commando Wiring Diagram – Richard Foster PNG 3066×1841
This is available as a PDF too – it can be downloaded here: