Effect on the Cooling System of Increasing Engine Horsepower
During operation, internal combustion engines convert the energy of fuel into mechanical work and heat. Approximately one-third of the fuel energy goes into the mechanical work required to make the bike move, one-third into exhaust heat, and one-third into heat transferred by the engine cooling system to the ambient air.

This means that heat load to the cooling system at rated power (Usually expressed in BTUs per minute) is approximately equal to the rated power of the engine expressed in BTUs per minute (HP X 42.4 = BTU/minute). From this we can see that if an engine is modified to increase its horsepower, the load to the cooling system will also increase. In fact, the heat load to the cooling system will increase by about the same percentage as the increase in engine horsepower.  So, if we increase the engine horsepower by 20 percent, we can expect an increase of about 20 percent in the heat load to the cooling system.