I did it on a speedster that I used to race with AARA in an effort to get the weight down (-see weight picture below). I used a motorcycle battery to power the ignition, and just removed the heavy starter, bulky cables and battery carrier, and the charging system to save weight. As I recall, it would run for quite awhile without the battery needing to be recharged. That engine had over 8:1 compression (I used a G28T propane fuel head) and I just hand cranked it every time.
FWIW, instead of being push started, a few guys put starters on their Model-A/B powered Big Cars (-predecessor to Sprint Cars) and used small lawn garden tractor batteries. As long as the engine would fire off in 3-4 revolutions during cranking, that battery would go all day w/o needing to be recharged.
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