The best way to tell is to use an optical thermometer.

The cylinder head measured at various locations, should not go above 340 or so degrees and typically a bit less.

If it gets above this you might damage or seize the engine.

With normal cooling after a flight your engine will be very WARM to the touch... warm enough to make you feel uncomfortable holding your hand against the cylinder head, but not so hot that it feels like you burned your hand.

When properly tuned and ventilated the AX is a pretty cool running engine, but you'll tend to load it up more on the ground than it will get in the air....

So it may run hotter on the ground... but it should NOT stop, smoke or give any other indications of overheating.

BTW: tighten the head cap screws after a good run. They come loose with the heat.