Ok everybody, i think i found the mistake, i checked the voltage that arrives at the auto-enrichener and i found nothing. There is the black wire and the green/yellow one. I checked the black one against ground and i had 12 Volts. So the green/yellow cable was not connected to ground (-). I connected a new cable to the auto-enrichener and grounded it at the frame. Now it runs like a V8 muscle car
Thanks everybody, at least now i know my scooter in detail
Markus