If the engine pops, spits, backfires through the intake, or requires you to pull the choke out slightly to keep it running smoothly, it is starving for fuel.

• Clogges main jet or passage: Modern fuel leaves hard deposits when it evaporates. Compressed air often isn’t enough to clear these. You need to run a soft wire or nylon brush through small passageways and jets.
• Vacuum leaks: The carburetor might be mixing fuel perfectly, but extra air is sneaking in. Spray carburetor cleaner around the intake manifold gasket, carburetor mounting flange, and throttle shaft while the engine is running. If you hear a change in RPM, you’ve found a vacuum leak.
• Restricted fuel supply: Ensure the fuel tank screen isn’t plugged with rust. Disconnect the fuel line at the carburetor and verify you have a strong, steady flow of fuel.