Take the carb off, take it apart remove all the rubber parts and let it take a bath in carb cleaner such as acetone over night then blow every passage out you can find with compressed air. Put it bag together and install and I will bet it will be fine. The fuel passages in these little carbs are so small it takes barely anything to clog them up and make the mower run out of whack.....Might as well replace the air filter and spark plug while youre doing work for piece of mind.