If you think you have bad fuel flow check it out first. If you don't have a shut off valve block off the fuel line as close to the fuel tank as you can ( clamp or vice grips). Remove fuel hose at carburetor and loosen your clamp with a container under the hose to catch the fuel. This will let you know if you have bad flow or not. I am taking a guess this is a push mower and has a fuel primer. Yes if you have been putting dirty gas into your mower you can well be having carburetor problems and need the carburetor cleaned.