I finally recieved my prop adapter, etc from wackerengines.com and everything fits fine.
I ran the engine with an APC 15 x 7 prop and I am getting 8500 RPM top speed. Alas, I can't get the engine to idle under 4300 RPM.
Heck, you can't land at that speed. Anyone know how to lower the idle on such an engine? It has a Zama carburator and both high speed and low speed screws are capped so not to be adjusted. The butterfly does close fully.

Any hints please?