It's not too hard to make your own. 14 to 18 gauge multi strand wire is available in most automotive stores, tho in limited colors. British Wiring can supply wire in many original color schemes. If you are not worried about stock appearance, you can use your imagination for alternatives to the bullet connectors. From Weatherhead connectors to simple spades.
A simplified diagram was printed in the original USNOA tech digest, but if you study the diagram from the factory manual, you can easily figure out how to eliminate a couple miles of voltage eating wire.
Adding a small fuse box with blade type fuses and separately fusing the ignition, lighting, and horn circuits makes sense at this point also. As does using small automotive relays to take the current draw away from the Lucas handlebar switches. With a little thought and fabrication, it can all fit in the original battery area.
I have done this on my 850 Interstate and along with a Podtronics regulator/rectifier and three phase alternator, has made a huge improvement in electrical reliability.
I'm a machine design engineer and do electrical diagrams (schematic and pictorial) every day. On my 72 I reworked all of the "front end" wiring using a small junction box with a terminal strip, etc., when I converted to a cafe style setup with a "pancake" headlight. I also added turn signal but used a new toggle switch on r/h side. I now wish I had redone the entire harness at the same time, but was itchy to get back on the road. I would like to replace more of the original junk with the podtronic, etc.
I'd be happy to do a proper diagram in autocad (can convert to pdf) showing upgraded components, listing newer (not bullet) connectors, proper fusing, available auto parts store part numbers. . . I've been using a new twist-connector scheme (of course I can't remember the name and I'm away traveling now). Can easily show differences in year-to-year changes. Would you be willing to collaborate on this. We can get together at mid-Ohio (I'm planning to ride out from Philly, but more likely on my BMW LT).
Speaking of wiring harnesses, does anyone have an electrical schematic for a MK III that they could post today?
I rode my Norton to a remote job site this morning only to have it quit running upon my arrival. I have no spark, lights or horn. So, I have some electrical troubleshooting to do in order to get home this afternoon. I’ve managed to scrounge up a volt/ohm meter and a few other tools here at the job site, but a schematic would be a huge help.
I've just finished rewiring my MK11A, Allens the Mikuni dealer in the UK do a handlebar switch for the lights, horn and indicators. It comes with about 20" of wiring attached. Cost me £28. The best source for the actual wire I found here is
They sell all the wires you could need in any colours you want so I used the colour codes from the Allen switch to rewire the bike. The crimp bullets they sell, code CB1 are really good when used with their crimping tool.
I have made a diagram but have no idea how to post it on the site.
thankfully i solved my current electrical problem which ended up being a bad spade type connector at the ingition switch.. simple enough. i still am going to get to work on design of a custom harness for future purposes. any help welcomed m
These are a couple of wiring diagrams I did for my 850 before starting to modify the wiring, they are basically a copy of the diagram in the Norton manual for 72/73 models with the Interpol wiring removed. 1972-73 Front 1972-73 Rear
Just thought they may be of interest to somebody out there!