L-O-LI would just buy a new plug and try it.
I can’t begin to count the number of small engines I’ve “fixed” with a new spark plug… and I can’t begin to count the number arguments heard claiming, “It can’t be the plug because…”. My dad, brother, friends and whoever… they bring ‘em to me time-and-time-again stating, “it won’t start” or, “it starts hard” or, “it won’t start after it gets hot” or, “it quits after it gets hot” or, “it don’t run right” or…
I always ask the same question, “Have you tried a new plug and fresh fuel?”
I always get the same answers/arguments, “It can’t be the plug because it has spark” or “I put a new one in it a month ago” or, “it ran fine last time I used it” or… And the same answers/arguments about the fuel, “It can’t be the fuel because it smells OK” or “I just bought it last week (yeah right)” or “my other engine runs fine” or…
The first thing I do is open the fuel tank (you wouldn’t believe how many times I’ve found it empty) and smell the fuel, check/clean the air filter, pull the plug and open my spark plug drawer (I live out in the sticks, I keep two or three spares for all my small engines so I usually have the right plug, or one close enough for test purposes). Eight out of ten times the new plug “fixes” it, but if it doesn’t I dump the fuel and pour in fresh, 9.5 times out of 10 that will fix it. I always get that “puzzled” look from them… like I’ve used some sort of magic or something.
Spark plugs are like light bulbs… you just never know when they’ll “go bad”. Often if the engine has flooded the plug has either been compromised, or even more likely is the root cause of the flooding… a flooded small engine automatically gets a new plug in my book (I’ve fought that too damn many times). I don’t clean small engine spark plugs anymore (fought too many times also)… for 2 or 3 bucks it ain’t worth the headache. I’ve learned, just because they throw spark in open atmosphere don’t mean cold squat…