Restarting these kickers can always be a bitch , One reason I went to E-starters. They spin over so much faster and blow clear the intake of extra gas in a hurry.

Usually it is an indication of a rich idle/pilot circuit , what happens is when you shut it off, it gets that last "woof" of fuel(besides having too rich a mixture already) but then it doesn't get burnt or passed through . Being the motor is hot the extra fuel turns to vapor and it fills the intake and chamber with a way too rich condition so no oxygen to allow ignition . They don't start till that extra vapor is flushed through and enough oxygen is sucked in . This is why many modern single 4 strokes have a hot start lever or knob , it opens a circuit to fresh air and no fuel so they start better.

Some things I did on mine beside leaning the idle circuit out as much as possible(but it took more kicks to start cold) was an aluminum plate that blocks the carb from getting so hot from the head/cylinder . When you shut it down I'd slowly kick it over till I heard the decomp click and leave it there . Also if you have a way to twist the throttle wide open so as it sit there is more area for the fuel vapors to air out. Don't ever hold the throttle open when kicking though , that can be a quick way to a broken ankle , these thing backfire with force.