1975 MK3 Commando indicator problem

Is the battery in good condition ? It's always worth checking and cleaning all connectors too.

Yes, definitely a bad earth. Using the frame as an earth is always fraught with problems. If you can, run extra earth wires from somewhere where you are sure you have a good earth, even going right back to the battery. And then onto the indicators metalwork inside the unit itself. 

Tony

If you think about it, you're trying to make an electrical earth connection between the forks and the frame- ie through the headstock bearings, which should be suitably greased and therefore isolating the forks!.A short earth wire from inside the headlamp shell to a nearby point on the frame would be a good start.

'do I need to run a separate earth for each indicator or will one suffice'.

What you are trying to do is create a low resistance path from the bulb back to earth. Using various bits of old and possibly rusty metal to do the job is never going to be optimum.

If you can run a wire from the metalwork of each bulb holder back into the headlamp shell and then one from the headlamp shell back to either a good clean connection on the frame itself or back to the battery. The you have a fighting chance.

You can do similar at the rear, the wires just need to go from the bulb holder metalwork back to something solid or the battery.

You could of course do one at a time until the problem goes away (for now anyway).

Tony

There is within the words above the idea that extra earth wires are run back to the battery-do NOT do it. I have always advocated a single wire to both battery terminals. Reason-if/when you remove the battery you only have one wire then you must connect that!! If you have several on one terminal then 'one' will get forgotten-something won't work. Or if you are really sloppy you have a spare 'blue' 'green' 'purple' wire which has no home on a battery so where do you connect it? You are bound to get it wrong and injuice smoke into the plot! On our bikes there needs to be a BRN/BLU on the Negative terminal and a RED on the Positive. ONLY.