Small engine primer bulb. The primer bulb draws additional fuel into the carburetor to help start the engine.
Fuel filter. If the fuel filter is clogged, it will restrict the flow of fuel to the carburetor. As a result, the engine may not start.
Fuel tank vent (also called a check valve). The fuel tank vent allows air to re-enter the fuel tank. If the vent is clogged, the engine may stall.