I've had nothing but trouble with Tecumseh engines, fairly good luck with Briggs engines and limited experience with Kohler and Kawasaki engines... between my brother and I we have worked on or had several dozen small engines, a couple Tecumseh engines have worked for a short time, most of the briggs engines run until something stupid happens (crank bearing goes out, valve seat falls out, plug threads strip out, etc). Many of the engines I've had are old since we do auctions and I'm a cheap bastage... We've learned how interchangeable most of the engines are, putting Magnetron coils on points engines and so forth.
My MTD/Craftsman blower has a Tecky single cylinder. It runs well, but the carb is shot, so it kinda has to be coaxed into do any sort of work. The PO left it with fuel in the bowl, and so the throttle shaft bore is worn, so it runs stupid. If I adjust it up so it isn't lean at idle it floods at higher RPM. That one also has the small square discharge, so it plugs easily.
My 11 JD that I just sold had a 19.5 Brigs, which wasn't a bad engine, never did have an issue with it, except the fuel shutoff solenoid. You gotta watch JD engines though, becuase they are bastardized so the internals can only be had from Deere.
My 65 WH has a K181 in it that still runs great. My biggest complaint there is that with the stock exhaust it is LOUD, with a cub muffler on it is much quieter, but that puts the exhaust right where I am sucking fumes the whole time I mow. It also seems like she runs out of breath at higher loads. It's fine running unloaded in 3rd, it is fine with the blades on in 2nd, but if I try to do blades in 3rd gear (I have some long straight-aways) she seems to run out of power. I'd like to find a 10HP K series to rebuild and put in it just for that. She also needs a new air filter though, and I am having trouble finding one.