Here a short update.
The last few days the problem of arcing trough the wires is gone (hope it will be in the future).
I always set the ignition as on the decal on the valve cover, 30° BTDC at 4500.
A few days ago i set it at 30° at 3000.
Since than the problem is gone, but i still can believe that this should be the cause.
Anyhow, the engine performance better and runs smoother, specially at idle it runs nice.
