I'm assuming the you have either a Briggs or Tecumseh engine, but the solution is the same. Start by carefully removing t.he bolt on the bottom of the carb. Try not to loosen the float bowl. This bolt is also the main jet, and will become gummed up over time. Clean this jet throughly and reinstall. Should do the trick. If it doesn't, report back with the unit and engine model numbers and we'll give it another try.