As with a lot of piston engines I seem to remember form a loooonnnnnggggg time ago if you flood it or get it over rich on a hot start try the following : mix lean cutoff, throttle full open, crank on starter untill engine starts to fire keep starter engaged while moving throttle to idle and mix to rich. The trick is to catch engine when the mixture is about right and that is when it will start to fire.
If you had a prop I would say turn backwards a few times first however not a option in your case.
As a bottom feeder in the early 1970's as a fitter it worked for me, now on the worlds largest "DYSON's" DC10 A300 etc and we do not have this problem it starts or not or catches fire!
Best of luck