Then look to your prop... what are you using?

It sounds like you have the engine in the right range, but are running a prop that is loading the engine down too much at the moment.

That may be why it is overheating.

Hows the cooling around the head? Is the head exposed?

On a pusher plane I had to use a lower diameter prop initially to get the engine fully broken in... After several flights I was able to revert back to a larger prop and not have the engine get too hot.

Note that normal operating temps ARE hot... but to be safe take readings on the head...

Remember that you do not want the measured temp around the plug to be more than 300-320 degrees.
The temp tends to climb VERY quickly beyond that, and once it does you risk seizing the engine... which can ultimately result in permanent damage.