I have a problem on my "other" bike. I hope nobody get offended if I ask here for technical support for a non Rumi motorbike, but in my usual Honda forum where I ask for technical help I can get solution.
The problem is a very annoying clicking/ticking/buzzing sound coming from my spark plug area.
This sound is not there all the time, but every time I use the bike it appear sooner or later. It came and go, not remain there once it appeared.
I tested many times replacing part by part with no result. I replaced the spark plug, the spark plug cap, the ignition points (and adjusted it properly), and also I replaced the condenser.
The bike run well, but this noise is driving me crazy, sometimes this electrical clicking is very strong.
When the sound started appearing some time ago I was thinking that was coming from the spark plug area, later I was the filling that was coming from the ignition points, but later again I think is coming form the spark plug cap area.
I ordered a cheap (copy) coil on ebay and I'll replace once it arrive, but if I carry on this way I'm going to replace all the electronic system with no success getting rid of this sound.

If any of you know about what can be the source of the problem for this electric buzz/clicking/ticking noise please give me a clue to test on my bike.
The bike is a Honda CB100 from 1970, engine is a 4 stroke, single cylinder, 100cc motorbike, 6V system.
Thanks in advance and I promise that I will keep asking Honda questions in the Spanish Honda forum that I normally do, not here, this topic is just a desperate exception.
Hugo