[Lynn Eades]

Not so sure.
An alternator does not have magnets in it and requires battery voltage to get the alternator charging.
A generator turned fast enough, will generate electricity enough to power the standard ignition system, from a completely dead battery ( 0 volts with a tow start)because the field coils are wound around soft iron pole shoes which contain residual magnetism. This magnetism is enough to excite (start) the generator.
I am not sure about the two brush geny, but the carrier manual (see picture below) states damage will happen, and advises the removal of the third brush in the three brush geny if you want to run the engine with the geny fitted, and not wired up properly.