[eagle]

A watt is actually a unit of measure for work done. Current (amps) X Voltage = Power (watts) Therefore if you double the voltage (from 6 volts to 12 volts) the current (amps) is cut in half in order for the same amount of work (watts) to be done. However, if you do not increase the windings of the starter, (use 6V starter on a 12V system) you still get the high amount of current AND the higher voltage. Therefore higher power (watts). Thats why the engine spins faster. This also can burn out the starter quicker because the higher watts creates a lot more heat. Fortunately the A starter is very heavily built so will handle the extra heat as long as you keep from running it too long. This is a very simplified explanation, there are other things going on too with 12 volt conversion but hopefully gives you a general idea.