Worked on Al's lawnmower that would not start after Winter (Feb 9, 2023). Using starter fluid or gas poured into the carb it would run for 3 seconds. Took carb apart and cleaned, no help. Found a good video on-line which showed how to take the carb further apart.
New plastic carburetor - easy cleaning parts teardown Briggs & Stratton Ethanol clogs - Bing video
After following the video and cleaning the ports with small wire and carb cleaner motor started great.
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Husqvarna Model 221A with Briggs & Stratten Motor 675EXI 163cc. (675 series)
Spark Plug RC12YC