This may be caused by the use of old/stale fuel. If untreated fuel is more than a month old, this fuel will start to break down and engine stalling (in addition to fuel system component gumming) can result. That's why it's important to either drain the gas from your outdoor power equipment before it sits idle during the winter, or add a fuel preservative/stabilizer to the fuel.

If you've got stale gas in your equipment, drain the gas from the fuel tank completely and dispose of it properly, following your local municipalities' regulations. NOTE: In most cases, this older fuel can be added to your car's fuel tank with no harmful effects.

Sometimes removing the old fuel and replacing with fresh, treated fuel may just solve the problem. If not, drain the old fuel and spray the inside of the fuel tank and carburetor with some carb/choke cleaner. Finally, remove any sediment from the fuel tank

Another thing to consider is that certain equipment manufacturers place a plastic packing plug between the gas cap and gas tank. In order for there to be proper venting, ensure that this plug is removed.