I think @Nevada_545 may be onto something. At the beginning of each mowing season I replace the air filter on one of my mowers that has a paper filter and on my other mower that has a foam filter, I wash it in a dishwashing detergent, squeeze out the soapy mixture, let it sit for a few minutes, pour a little motor oil into the foam, squeeze out the excess oil and it’s good to go. I picked up a used mower for $15 that ran poorly, so I added carburetor cleaner to the gasoline-- I think it was GumOut. It did the trick for that mower.
We have had a very mild winter here in east central Indiana. I haven’t had to use my snow blower once. Our grass is beginning to green up and the crocuses are blooming, so in three weeks or so, I am going to have to get our mowers going. We had such a late fall that about all I could do when I put the mowers away for the year was to fill the gas tanks and add a fuel stabilizer.