Hello people, I so often ask for help from this forum...well just for once maybe I can give some useful information about a really mysterious problem.
Got on, turned the key - the three little lights came on as they should. Pushed starter - engine starts and runs perfectly. However, nothing else electrical would work (apart from the brake light). No headlight, no parking light, no dial lighting, no horn, no turn indicators, no tacho. First thought: must be a fuse. But both were fine. I was a bit concerned over earth (ground) connection as just about everything at the front is earthed through a single point, shown on the diagram next to the speedo but in real life I could not find it anywhere. However a check with the test meter buzzer from the earth connector in the headlight down to the frame gave a good loud buzz from a closed circuit, so nothing there.
So tank off and try and identify any likely connections and test them. All seemed fine including supply to both headlamp filaments.
Well in the end the light bulb over my head lit up. Funny you know, politicians here always blame any problems on "the previous government", well us bikers blame things on "the PO". Sure enough, a PO had fitted the front coil to the frame using a clamp which was too big so the coil had swung down and was bumping on the engine casing. I fitted a better sized clamp and then noticed a brown earth lead on one of the bolts. I guess this must be all you can see of that multiple connection shown on the diagram -- and my new clamp had an insulation liner. So no ground to frame, and there could not have been one through the oversize loose clamp (and the paint). Rigged up a temporary lead (now permanent) and problem solved.
Left with two puzzles: why did the test meter buzz happily, and how was the original coil fitted by BMW - there's no sign of any mounting.