Hey,
Overheating is a relative term. In the case of liquid cooled bikes, they will boil the coolant out. In the case of an aircooled bike, nothing happens, until you literally burn up the piston and/or warp the cylinder head. I've had several aircooled XR's here in Florida, they run really hot, but that's about it. Never did have a problem. Keeping fresh oil in your motor all the time is one of the best ways to keep an aircooled bike in good shape. Good luck.