Hey guys,
I finaly ordered OEM screws from Yamaha because my old ones where crapy.
I allmost did not manage to get them out. Carefully turning and WD40 helped.
As an advice everybody with a Z should try to totaly unbore the screw and greese it. But I bet that the most Z drivers would not get the screws out without force because of corrosion inside the swingarm.

Cheers
Marcus