ahh - my bad - i thought it was 80 hehehe =)
Yes, i have an adaptor that Mike made up for me, but my motor is not quite so large, at only 44mm diameter (vs 50mm), and with 30mm hole circle... it will depend on the hole circle of the 5090 (i called it bolt pattern before - either or :))
http://www.lehner-motoren.de/ms22_mas.php
Maybe email them to check , and if you have any dramas, get the specs and i'm sure Mike can make it up for you =)
btw - the adaptor is 44mm diameter with the 30mm hole circle, so you may need a 50mm diameter adaptor with XXmm hole circle :)