Of course it depends on the particular aircraft. Hand-starting my Champ with fuel turned off then allows just about enough time to take the chocks out, walk round the struts, stow the chocks, climb aboard, and get my harness sorted out before the engine dies; and that's at approx 750 rpm. Taxi and power checks? No chance. But I would not assume any other aircraft, not even another Champ, to be the same.