I talk about how to fine tune a RCGF 15cc petrol engine. Taking it up to maximum rpms, and then richening the engine further so that the rpms drop by about 200. By richening the engine this way, it should not be too lean in the air.
If you tune it on the ground without the slight richening, ie, just tune so that the engine is running at max rpm, then it will run too lean in the air and overheat.
Finally, if I was to tune the engine by ear, I would over richen the engine by about 500rpm. It is only a fraction of a turn to the engine down by the recommended 200rpm.
Obviously, I will need to test the engine in the air, retune on the ground, and test in the air again. This was just a bit of fun while waiting for my next flight.