It still could be vibration causing a frayed wire to short to earth, but...

It could possibly be a dicky voltage regulator which is causing over voltage? Does your headlight seem abnormally bright? Does it get significantly brighter when you rev the motor? Does the dash backlighting vary in brightness with engine speed?

If you have a multimeter then check the voltage across the battery terminals with the engine (and ignition off), then at idle and finally when reving the engine at >4000 rpm. Let us know what the readings are. You should not get more than 14-14.4V even when bouncing the motor off the rev limiter.

It could also be a failed diode(s) in the rectifier (part of the same unit) causing AC voltage to leak through into the system which can get as high a 60V off a three phase alternator. The above voltage check should highlight either problem if it that.

__________________