Improving an Overheated Cooling System
Armed with this understanding of how a cooling system works on a MX Bike, what recommendations should we make for a cooling system that is overheating?  Suppose we have a 250F engine and cooling system that, in stock condition, produced a rated 34 hp and ran at rated ambient temperature with An inlet tank temperature of 190 degrees F and a 10 degree F temperature drop through the radiator.  Now suppose the engine were modified to produce 39.8 hp, a 20 percent increase.  We would find that at 39.8 hp the core temperature drop had increased by 20 percent to 12 degrees F and the top tank temperature had increased, let’s say to the point where it was just overheating. 
Now suppose we take this system and reduce the power to the point where the radiator inlet, or top tank temperature is steady at 190 degrees F. 

(Guess what?  It’ll be producing 34 hp! ). So we check coolant temperature drop and find it is back to 10 degrees F, as we would expect, meaning the average core temperature is 185 degrees F.  Now we want to make improvements to the system in order to lower the inlet tank temperature to the point where we can then go back to 39.8 hp without the engine overheating.