Mass ... and not like a fat guy doing a bomb in the pool. But mass as in the story that 'stream' must be able to flow. From one battery pole to the other.
Mass: Then we are in the electricity corner
A wonderful world where classic lovers are still lucky enough to be able to see and follow threads instead of looking for the secrets of dead electronics in surprise. But electrical things are still tricky business for many of us.
Like New. Is kind of good
A top restored classic is of course ZGAN. But in his time even "new" was no guarantee for anything. In the background a couple of Italy lovers burst out in desperate howl. They run laps and bump their walls against their foreheads.
Someone once noticed that his brand-new Benelli Sei was horny when he sent to the right. When steering to the left, the indicators went on and smoke came out of the headlight. With my own Guzzi I just had to pull a handful of smoldering cables.
Check step by step
If there are electricity problems, first check whether the lamps in question are still good. Then check the fuses.
Subsequently, there may be wire breakage, insurmountable transitional resistances or a mass problem. In practice, one of the last things is often the case.
Easy to check
But checking the masses is nice and easy. So we start with that. There are a few things that are often the source of misery: the connection between the minus of the battery (with a few old British bicycles the +) and the headset. See if things work again if you make an improvised connection between the battery terminal and a blank piece of frame or block. If this is the case, you can simply make an extra connection between the battery and the frame with a braided mass cable, such as auto material shops that sell in a range of sizes.
The same story can be true for the voltage regulator.
For a number of motorcycles, the steering head and the steering head bearing provide (part of) the mass connection between the frame and fork. Steel balls embedded in thick fat are not the ideal conductors. Also look here again what happens when you make a good electrical connection between the headlight housing / front fork and the frame.
The classic in the photos is used almost daily and is more focused on effect than on beauty. The repair is done with available resources. Improvised and rude. But it works masterfully.
Then check the plug connections.
Internal corrosion causes resistance. And if a plug (block) looks like it has a nasty form of eczema, then that can be a clear reason for 'the power' to see such a connection as a lock with closed doors.
Buy a spray can with contact cleaner and / or try to clean the contacts mechanically. But that is usually a breeze. After-blowing with compressed air. And in the absence of a compressor, this can also be done with a spray can. You can find those kinds of spray cans at photo shops or if you are lucky at the Action.