questions about "Master Switch"

1972 Commando. I have a Master Switch that doesn't seem to fit the rear air filter bracket correctly. I did take it off but want paying attention to the fit. It seems to be too large a diameter (1.58" or 40MM) The Bracket has a 5/8" hole center which would put the Max Dia of the lock barrel @ about 1 1/4". It is hidden behind the sheath but there is another problem.

It only has 3 terminal positions, 2 doubles and a single. No Blue/Yellow wire in the old harness. Has a Norton style key. I'm wondering if it is a Norton part. Certainly same manufacturer.

Hi Brian, There should be a long spacer behind the bracket taking up much of the thread. Not sure it's available separately, buy you can see what I mean here...

https://andover-norton.co.uk/en/sho...6-2846-06-6625-12-1015-19-1269-92-1498-39784-


Hope that helps,

cliffa.

Thanks Cliffa. It has a threaded nut to set the depth, and I can twist the bracket a bit to make it "look" ok behind the rubber sheath. It appears to be the part, but the lack of the 4th terminal is puzzling.

The spacer is missing.

brian4.2 said:

the lack of the 4th terminal is puzzling.

Click to expand...

Early '72 models (prior to 202116 apparently) still had the three-terminal (39565) switch and no blue/yellow wire.

From looking at your pictures it appears as though you may have an earlier Fastback rear air filter plate. The ignition switch bracket on these earlier plates was designed to work with a smaller diameter ON/OFF switch.

The four terminal ignition switch along with the blue/yellow wire was added to the later motorcycles so that when the ignition switch is on the pilot light position, you would not be able to turn the headlight on, only the pilot light, tail and instrument lights will illuminate.

Peter Joe

Thanks, My new harness has the blue/yellow wire, just leave it out? I will be upgrading the headlight somehow.

brian4.2 said:

My new harness has the blue/yellow wire, just leave it out?

Click to expand...

You could connect blue/yellow (UY) to master switch terminal 3 along with the brown/green (NG) or, connect the headlamp switch UY to NG at the main junction area below the fuel tank otherwise there would be no power supply to the headlamp (headlamp switch).

Perfect thank you, that's what I needed.

I will need to do it under the tank, the NG at the switch is the single blade terminal.