Welcome!
While it's possible is may need the valves adjusted, it sounds more as if the carburetor may be a little dirty, and or the gas it's running on is stale. If it did not run like this before, it is probably not valvetrain related then. I would suggest running it as it is with fresh gas for two or three more mowings and see if it clears itself out.
If it still persits to run the same after a while with the fresh fuel, then pursue cleaning the carb.
Also, something you may already do but thought I'd throw it out there anyway, if your machine has a valve on the fuel line, run the fuel out of it before winter and also inbetween times when it's not going to see a lot of use for a while. This will run the gas out of the carburetor so that there's no fuel sitting in it to potentially gum it up.
While it's possible is may need the valves adjusted, it sounds more as if the carburetor may be a little dirty, and or the gas it's running on is stale. If it did not run like this before, it is probably not valvetrain related then. I would suggest running it as it is with fresh gas for two or three more mowings and see if it clears itself out.
If it still persits to run the same after a while with the fresh fuel, then pursue cleaning the carb.
Also, something you may already do but thought I'd throw it out there anyway, if your machine has a valve on the fuel line, run the fuel out of it before winter and also inbetween times when it's not going to see a lot of use for a while. This will run the gas out of the carburetor so that there's no fuel sitting in it to potentially gum it up.