I have similar experience with gunked up parts and some engines sitting for long periods of time without use working without issue... I have a little Homelite XL saw (the little 25 or 30cc guys with 9" or so bars) that I got at a garage sale for $5 probably 7 years ago, it ran good when I got it but the chain was sharpened unevenly so it would only cut about 2" before getting stuck... Anyway, that saw sat unused for ~5 years, pulled it out and it ran like a champ still, almost always starts within a few pulls (except last night, was stubborn but was 25* outside...). I have an old Homelite 540 that I got cheap, wouldn't run, had a dried out regulator/metering diaphragm so I stole one out of a running weedeater, that sat for 5 years without running also, started it up a while ago and it runs like a top with that same diaphragm...

I've also been the "gas guru" with the broken plane from a failed diaphragm at the field...

I've had best luck keeping fuel in 2 strokes, and running 4 strokes dry, but I usually forget and leave everything with fuel in it...