Hard to start after stall

could be a fuel flow problem or perhaps it is too rich to run after it is warm

to check flow - take out the drain screw on carb bowl & watch fuel run into a container under the hole to see if it seems sufficient

check richness as usual be reading plug or just trying with needle lowered to see if it helps

Also 20:1 is awfully heavy. This topic has been beaten to death here switch to 32:1 as well and that could what's wrong. Could be fouling out the plug.

Yup... I was going to say something about the mix ratio being too heavy with the oil... 32:1 is perfectly safe for break in as well as helping the engine run just a tad cooler from the richer air fuel mix...

Also check your spark plug gap if you haven't already... these engines tend to start easiest and run best with a gap around. 022" to .024"... if the gap is wider than this it will become hard to start. Also the factory plug is junk so get a decent plug like the autolite #275 or an ngk plug... this topic has been gone over a lot as well so someone can chime in and tell you the ngk part number. No real need to buy an expensive irridium or platinum plug during break in but its optional afterwards for better reliability.
The other weak spot in the ignition system is the stock spark plug boot... replacing this with an automotive type boot and installing the little metal contact cap on the plug will make this area a lot more reliable.

try venting the fuel tank , by leaving the fuel cap loose . if this works , you need to drill a small hole in the top of the cap . some of the caps don't vent well

Check your clutch cam, these tend to wear out causing the issue... The clutch cam can be easily removed by turning the clutch arm while gently pulling it away from the clutch cover, they're usually coated pretty good with grease so they do need a good cleanup to inspect, but you'll notice the area that wears out and if it looks like that edge has been rounded down it's time to replace the cam.

Ha ha ha ha ha what a joke all these replies...hahahahaha your motor aint run right unless you are prepared to spend 20 to 30 bucks a gallon on non ethanol fuel for small engines. right now, you are burning butane and ethanol . Thats no good for small engines, 2 cycle and 4 cycle . this crap gas you runnin will start to destroy your engine in 30 days... and nobody here mentioned it. hahhahha what a messed up joke... in outa here,. time to go electric and forget about all this messed up crap gas