mk3 wiring

Avoid the cloth covered variety of harnesses available. They are far too stiff to get packed around the frame properly, and they hold all the oil and shite the engine expresses. The correct and better covering is the pvc tape wrapped ones (like from AN)

Personally i prefer to make my own harnesses and if your bike has electronic ignition (like most of these bikes have now) you can tailor the wiring to suit, getting rid of the silly block connectors and ignition sub harness under the tank. Putting all the forward connectors in the headlamp shell. Makes for a much more reliable set up.

Be aware that what ever make of harness you go for you will probably have to swap some connectors as what was fitted 50 yrs ago could well have changed between then and now. I fact it is a good idea to change all the connectors that the harness will plug into as they are well past their best by now.   

Worth having a look at Grant Tillers website. A lot of useful information including about the modern replacement wiring looms.

https://granttiller.com/lucas-wassell-1970-74-norton-commando-headlamp-harness

Apparently there are a few versions of the harness due to several reasons. The 'modern' style plugs and sockets at the front of the harness differed in the short life span of the MK3, some don't have some of the plugs at all. I once asked and had photos sent to me and they all differed. 

The best bet with a MK3 is to either adapt an off the shelf harness or starting with Grant Tillers website and build one to suit what you will fit as it will allow you to miss out the cables no longer needed and add in ones that you may want in the future for accessories like phone or satnav.

With a MK3 the most important cable is the engine earth return, this must be fitted first so you don't forget it. With it not in place, if you accidently lean against the start button you will smoke the loom. 

I always use TMS for my mk3 harnesses & have had no issues - UK made & I think AN uses the same source (but don't quote me on that). I use a star point for the red earths so that the only red cable to the battery is the large one from the engine casing.

I sell a wiring kit. This has all the correct colour wires and basic Lucas and Bullets. And PVC tubing but no block connectors. The basic kit is not for MKIII but can be adapted.