It sounds like your engine is probably in a cowl. If this is the case, you will typically need to have proper ducting and intake/exit openings to ensure it doesn't overheat.

Personally, I have never taken a temp reading of any engine I've ever owned. I very quickly pinch the fuel line. If it speeds up I lean it a little until pinching the tubing does not increase the rpms. If the rpms drop when pinching the tubing I richen it immediately as that is too lean IMO. I also use a tachometer sometimes to find peak rpm and then back it off a few hundred. The only engine I ever damaged from a lean run was the very first one I ever owned - a ringed K&B .40 - and I had no idea what I was doing back then.

David