you can take off the pull start and leave on only the one way bearing
then get a hex nut key that applies to an electric drill and drill it clockwise from behind the engine

maybe that is sci fi though

what I did when my pull start spring broke and i couldnt fix the spring, was to remove the whole thing except the one way bearing. put the wheel back on (without the cover) and start turning it with your hand until the string rolls back to place. then pull as you would normally. it works perfectly but you always need to roll it back in manually. offcource when the engine starts remove the wheel and the one way bearing.
note: dont start the engine backwards.... the wheel should turn clockwise as you try to start it

hope you make it