'73 Norton Commando

Hi Folks, Just acquired a 1973 Norton 850 Commando (wanted one since I was at school). It is in good condition mechanically but I am not getting any power. Old battery was dead so I put in a new one and it is charged and ok. Getting power to the ignition switch and I checked the switch for continuity. Also checked the fuse and it is fine. When I turn the key to the on position I get nothing. No lights, no start, just dead. I have a manual on the way but wanted to check with you guys to see if you could point me at where to look next. Be gentle with me, it's my first time.

Welcome to the forum. I'm sure you will find all sorts of help here. As a start, you might just try tracing the 12 volts along the path to the coil. First point is at the ignition switch, and it sounds like you have already measured 112 volts at the input to the switch, and the ign output terminal. From there, it runs through the handlebar switch to the ballast resistor, to the coils. The easiest check is probably just to look for power at the ballast resistor. That should be at the white/yellow (or maybe white/blue?) wire that goes to one side of the resistor. If you have voltage there, the next point to check is at the coil input terminal, which has white/purple wires going to it. The voltage there should be less than 12 volts, because the ballast resistor drops some of the voltage. If that's all good, the next place to check is at the points, where you should get voltage when the points are open, and none when they are closed. That should get you started.

This is a wiring diagram for the 1972 - 1973 Commando:



Ken

Just noticed that there is a nice discussion of the '73 wiring diagrams and wire colors here, that might be helpful to you.

https://www.accessnorton.com/NortonCommando/73-oem-wiring-diagram-question.27202/

Ken

Two areas that need to be checked and serviced on all of these bikes, the kill switch and the large rubber connector under the tank.

The kill switch is a set of contacts points that are normally closed. Any corrosion there will kill the circuit. The rubber connector is full of female bullet terminals that have a tendency to crack with age.

The ignition switch might have continuity but be corroded enough not to provide a good circuit. A jumper wire to bypass it would tell you right off.

The below was done by a member here to help with the color identification. It might be hard to read but I could email it.

There are manuals available online. Links are available in the technical section of the forum. Below is a link to one of them in .pdf format. I downloaded one to my computer and actually use it more than my paper manual.

http://classicbike.biz/Norton/Repair/70up_Commando/70upCommando.pdf

I'd suspect the ignition switch first. Mine was unreliable in the "run" position and needed restoring or replacing. Try making a bypass to confirm if your switch may be faulty.

I see some corrosion evident around the kill switch. I'll start there. Thanks for all the really useful information. I will keep you posted.

Tornado said:

I'd suspect the ignition switch first. Mine was unreliable in the "run" position and needed restoring or replacing. Try making a bypass to confirm if your switch may be faulty.

Click to expand...

Second that.

Roboticpete, it would be helpful if you could tell us if your new bike has points still or has been converted to an Electronic Ignition and what kind?
Does it have the original coils up under the tank still?
Have you removed the old spark plugs and installed some new NGK BP7ES or the proper resister plugs if you have an EI? Just thinking of your no ignition issue in case you do get power forward but still no sparking with the plugs pulled and grounded on the head while kicking in dark garage to see if spark.............

And the obvious question is, are you aware that these bikes are positive ground?