Actually, a single 9v alkaline cell will run a 200ma computer case fan (about 35 cfm) for at least 4 hours. A fairly inexpensive rechargeable 12v NiMH pack would run it for well over 10 hours straight, and LiPO's will do much more. The temperature may not be specifically quantifiable, but it won't boil with a normal high quality EG or PG coolant mixed at 50/50 under a 16 psi cap running two such fans. Add a handlebar
switch and turn it on only when called for, or get fancy and install a thermostatic switch.
There's nothing super secret about Evans
(also sold as Zip-Ty) coolant. It is simply a mix of glycols, predominantly propylene glycol, and formulated to be run without water. You can, in fact, run most fairly ordinary coolants, PG's in particular without water and get a higher boiling point by doing so, but you run the engine hotter because of it, since the plain truth is that plain water with a surfactant added cools better than any glycol coolant, straight or mixed with water can. The only thing really different is the slightly lower viscosity that allows it to circulate more freely. It actually will not keep the engine as cool as a mixed coolant or water will as long as there is adequate air flow and coolant circulation, and boiling is controlled, and I saw nothing on their web site suggesting otherwise.
I did see kind of a "Captain Obvious" moment, to wit: "In a 100° F environment a radiator that is 250° F will dissipate 25% more heat than one at 220° F." Well yes, the greater the temperature difference between the radiator and the air, the more heat moves to the air, but so what? Is there then supposed to be an advantage to running the engine hotter in order to shed more waste thermal energy into the air? Understand that this is exactly the same as saying that a radiator at 220℉ in a 70℉ environment will shed 25% more heat than one in a 100℉ environment (with the same shaky thermodynamic math). Following that logic, it would be better, I suppose, in 100 degree weather, to run the coolant at 300℉, since that way the radiator could dissipate 67% more heat than it did at 220. Somehow, I don't feel inclined to do that, but maybe that's just me. Interesting sales pitch, though.
The YZ450 does not overheat when used as intended unless it has an addressable mechanical fault. But it is not intended to operate for extended periods at low speeds, and is therefore not equipped, as built, with the one thing it needs most in order to replace that which goes away when you slow to a crawl, and that is a way of providing air circulation over the radiators. Fans fix that while leaving the rest of the system and its designed temperature range intact.