thanx to Hamburg for extended info. i knew this more-or-less, just hoped somebody had discovered a loophole somewhere; "for private use only", "experimental", "for testing" etc 😅 had hoped that without modifying structure or safety there could be one ... the bureaucracy in EU is...
I am searching for someone who has already done this here in Spain - EU: take a street-legal motorcycle and change petrol-engine for electric motor. with DIY battery.
i thought it could make a difference if i don't exceed original power and leave everything else -brakes, wheels, lights etc-...