MAybe the float in the carburetor is set too high?
Wouldn't make any difference, the float just controls the fuel going to the bowl, not on the running of the engine.
Those old lawnboys are bad to leak fuel from the carb onto the deck in such small amounts at a time it dries up as it leaks out the carb. The air filters are the same color as the fuel mix when you check them. There is a stain on the deck as well. Just shut the fuel off when you park it.