4 strokes w/out muffler, anyone else?
I would suggest doing one thing after you stop the engine - turn it over slowly by hand until you feel the compression resistance. This will put it in position with both valves closed (seated) which allows the excess heat to be conducted, closes off the ports to dirt and bugs, and helps to keep your valves symetrical and takes the load off of your valve springs. The alcohol gokarters do this religiously.