This has been done many times, usually not very satisfactory in engins less than 1 cu. inch. You have to change the carb (regular glow orfices and needle valves allow to high a flow rate making them difficult to adjust) and add the spark plug in place of the glow plug then add either electronic ignition or a magnetoe (an expensive addition). Probably not worth the cost and time unless you just like to experiment which can be good and self rewarding.