Electric motors and generators aren't perfect machines and even if they were, they would only have enough power to turn themselves. The best motors on the market are close to 90% efficiency. Also... generated power is not free. To test this, take an alternator from a car or perhaps any toy motor (motors spun extranally act as generators but not as efficient) and spin the shaft quickly with your hand or a string. It will spin as freely as the bearings will allow. Now place a wire across the two leads. The wire is the load. Attempt to spin the motor and the faster you spin it, the faster it stops. The more power you generate, the more draw from the load. In this case the wire is a dead short and will draw enough power to melt itself down if external force is constantly driving the generator. So to answer this: The 90% efficiency motor Attempting to generate power to drive a 90% effciency generator will basically need 20% extra power due to the loss from both devices. (the actual inductive equation is far more complex than that. I used the #'s more as symbols) And the more load on the generator besides the motor will drag the generator down even further (like the wire load on the generator) So even if the motor and generator were both in a vacuum without gravity or bearing load and were both 100% efficiency, The 1st load applied no matter how small would eventually drag the motor and generator down to zero speed.

If only it was that easy, but there is that many losses through motors and generators e.g friction, copper loss, iorn loss, hystersis etc that they just cannot power themselves. Perpetiual motion like that and perpetiual motion were the losses can be overcome enough to do somthing with it is one of the holy grails of science. nice thinking but

In practically everything you do, some of the energy used is lost as heat. For example, you may have a motor which uses 1000 Watts of power. But some of that energy, eg 100 Watts, is wasted as heat and so that only leaves 900 Watts to run a generator or two. But the generators waste a bit of energy as heat, say 90 Watts, which leaves 810 Watts with which to do any work with. So your 810 Watts will not be enough to drive your 1000 Watt motor. If you try to do anything else, that will take away even more Watts, leaving less again to drive your first motor. Energy is lost other ways too. For example, the noise the motor makes is energy lost.