I tried an experiement with zapping magnets and the magnets became strong with in a few hours of the process. How I know they became strong I tested the kv using the generator method where you connect a drill and spin the motor shaft at a give speed and then check the voltage at the terminals. The voltage at the terminal increase on all the motors I did the zapping experiement on. This is how it goes. First wrap a long piece of coil around the out side of the magnetic field on the can when you have it properly wrapped it would cover the entire lenght of the magnets. Secondly connect each side of the coil to a switch then connect a power supply ( battery pack ) on the other side of the switch. The idea is to short out the battery through the coil. Use the switch to control how long you short out the battery. Don't allow the power to flow longer than 1 second or even half a second at time. It's really quick bursts of high current through the coil. This method strengthen the magnets of two 700bb motors and a 290/30 series plettenberg.