Rolf asked: "what is about your depolarising electric system?"
My R27 still depolarizes itself. It has a new Huggett generator, rotor and both mechanical and electronic regulators have been tried. It ran OK with those new parts for a year, then it began to depolarize.
It only happens when the headlight is on and the engine drops to idle. Then the generator light pulses (flashes) and will not stop flashing until the generator is repolarized.
It was very inconvenient to repolarize by touching a wire from the battery to the generator, so I connected a horn switch to the regulator and mounted the switch on the coil. Now when the red light flashes, I move to the side of the road, reach under the tank, and push the switch for a moment to repolarize the generator. I only have to do that if I am using the headlight and the rpms drop to idle speed.
Because Guenther and I cannot solve the problem, I am having someone make a 12V system for the R27, using an adapter ring to mount an alternator from a /5.