I didn't mean that rich would hurt the engine, so correct, it's not "bad" for it. But it is bad for flying and will make for a poorly running engine. If there aren't any air leaks and the fuel delivery is good, then there's no reason not to run a properly tuned engine for best power and throttle response. I see guys at the flying field regularly running their engines too rich, either because they don't want to bother with them or because someone told them that always running rich is better.

downunder- no offense intended. You post likely was spot on for the thread it came from but for a new flyer learning to tune it would lead to problems. The best treatment of an RC engine is to be tuned with the mix just right, which the general consensus says is about 300 rpm rich on the test stand or max power with the nose pointed up. There's no reason a flyer needs to tune any other way once break in is done.