How do I increase 2.2kva generator output and can I use electric motor on generators instead of petrol motors

If you are hoping to achieve perpetual motion, give up on this arrangement. That would require energy to be absorbed into this system due to heat and EM losses.

However, besides this fact, anything that can spin the pulley on the generator can produce power.

You can increase the wattage output by increasing either the Amperes or the Voltage. The voltage can be stepped up by the number of windings and the speed of the generator, in DC. In ac generators, the speed is in direct control of the frequency. The amperage is probably the smarter thing to increase. A stronger magnet will allow more amperes to flow and so will a thicker wire in the windings.

There are other things to consider here also. The more you step up the amperes, the more torque is required to spin the generator. Secondly applying more amperes requires you to adjust the load accordingly. If you load is drawing more amperes than the wire in the windings can handle then you will short them. If you increase voltage by adding more windings, you are also increasing the resistivity of the wire within the generator, thus becoming hotter or less efficient in other ways.

And for reference, increasing the frequency in AC generators does increase the overall energy, but not in wattage.

If you are going to change the windings, you may as well buy another generator.

If the load is a motor and you want more power to get the motor started, you could use capacitors to improve the power factor of the load, thus reducing the current required to drive the motor.

If you are just running lights and such, there is not much you can do.

If you are running a fridge or an air con, you will need a generator about three times bigger than the run current of the motor as you need to overcome the high strting current of the motor.

UNLESS you use a soft starter of VF Drive, in which case you may as well just buy a bigger generator.