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My 1978 R100/7 may have an ignition switch problem. Sometimes when I turn on the key I have nothing, sometimes I hear a crackling sound in the headlight, sometimes everything is fine. When it is not working (nothing or crackling sound) I have removed the headlight and just wiggled the wires at the ignition, by that I mean just inside the headlight box from the key, and sometimes this fixes the problem. Any thoughts?

That may just be corrosion on the wiring connectors. Cleaning the connections on the wiring may fix your whole problem. If so, cover the contacts with dielectric grease after cleaning them, and they won't ever corrode again.