Hello Rigger:
If your down exhaust pipe is Straw Gold color, sport that around and be glad. That is an indication the engine is running at optimum efficiency and temperature.
I read a study on the bullet mania web site from the UK, by a chap from Oxford about, the role of fuel mixture and possible over heating of these engines. I believe he is a bullet owner. After some testing under real riding conditions he concluded that a more moist fuel mixture charge entering the engine gave a mili-second of cooling during the intake stroke and more importantly during the compression stroke before the spark plug fires the fuel charge which raises the engine temperature. The fins can only do so much to cool the head and barrel. He felt the wetter charge did just enough interior cooling to keep temperature under control under normal riding. If the fuel charge is too lean, very little interior cooling of the head and barrel under the same circumstances would lead to excessive heat, bluing of the exhaust pipe, and possible seizure.
The proper fuel charge with enough moisture can make the difference between normal engine temperature and overheating. The moral of the story is, don't run your bike when it is too lean or you will risk too high temperatures in the engine and bad results. Riding it too hard consistently at too high speeds can do the same thing.
If you suspect the engine is too hot, stop and smell the bike. A hot engine has a distinctive smell which should tell you to get off and let it cool down before you resume riding.
Don't ask me how I know !
Neil
ps. I ride Buzzy a tad rich. gas mileage is acceptable and a new plug to start out each year is not too steep a price for a cooler running bike.