If your bike is getting hot and you never notice the radiator fan engaging, there might be something wrong with the system. Fortunately, it is very easy.
The radiator fan is run by a simple DC motor. This means that you can just provide power and ground to the wires, and it will run. That is how you test the fan, using two wires connected to your battery. Make sure that the wires are connected properly, it won't hurt the fan if you switch them, it will just rotate the fan in the opposite direction and it will blow air away from the radiator and be useless.
The fan is actuated by a thermostatic switch, basically a heat switch. It closes a circuit when it rises to a certain temperature. If your fan and wiring is good, then the switch might be seized. Here is how to test your switch:
