This is as per the Power Arc electronic ignition diagram I have detailed in the post prior to this.
However, the diagram has also been amended to accommodate the MC2 dual output single coil that is sold in the Old Britts kit.
The MC2 coil is a little unusual in that it features a continuous supply, but has a third terminal which triggers the coil on and off (most coils have just two terminals)
My diagram is a little different to Fred and Ella’s.
Fred has taken a separate -ve fused feed directly from the battery for the MC2.
This means that the coil is not powered down on the ignition switch, something that I personally don’t like.
I have, instead taken the feed from the white wires in the main connector block (which is situated right next to the coil location anyway) so it is therefore de-energized when you turn the ignition key to the off position.
I could have tee’d into the blue/white that comes from the kill switch, however it is in our interest to lessen the load we put through our delicate handlebar switchgear as much as possible!!!
Here follows the wiring diagram for the Power Arc electronic ignition + MC2 coil.
Pre-1971 (ammeter in the headlight shell and Wipac Tricon type handlebar switch) PNG 3066×1841
1971 (three wires to the master switch) PNG 3066×1841
1972 onwards (four wires to the master switch) PNG 3066×1841
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.
These bikes are also wired with the old Lucas 3AW 3 wire ‘silver can’ assimilator.
1974 MK3 (Early) PNG 3066×1841
1975 MK3 this is the most common configuration, and takes us through to the final Commando that rolls off the production line.
1975 MK3 (Original) PNG 3066×1841
1975 MK3 Canadian Market – there were legal requirement in Canada around the headlamp being on while the engine was running, so the wiring diagram includes changes needed (swapping out the Warning Light Assimilator 06-6393 for the Headlamp Warning Unit 06-6392). Note that a different Master Switch is also required.
This is covered in the Factory Wiring Diagram, by notes.
1975 MK3 (Canadian Market) PNG 3066×1841
A couple of points about the way these diagrams have been drawn:
- 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
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