What you feel is probably the hot air from the radiators, combined with friction from moving on the seat. There is no way the seat can get hot enough to be uncomfortable from engine heat. The fuel tank and airbox form very large insulators. If you don't do it now, try the Moose undershorts (like lycra bicycle shorts) and some butt grease. Its gross, but works!
For a real nut roasting experience, you should try a Cannondale 440 (with rear exhaust and underseat header) in mid summer.
