[Al Skierkiewicz]

Jose,
This sounds like a good idea except that a capacitor for the most part will lose it's energy fairly quickly. You need to remember that the motor is a very low impedance. When you connect the cap to it, a large amount of the charge will be dumped instantaneously while the remaining charge will dump out over time. Check out capacitor discharge curves and time constants in a reference. The ARRL Radio Amateurs Handbook is a great source for this and is available at most libraries. The amount of current available and the time of useful discharge are a function of the load impedance (resistance) and the cap internal resistance. To make this effective, a bank of several capacitors may be needed, which gives diminishing returns on energy vs. weight for your application.