Fuel System Issues:
* Empty or Bad Gas: The simplest reason is that the engine is out of fuel or has stale fuel.
* Clogged Fuel Line: Dirt or debris in the fuel line can restrict fuel flow. Check for any kinks or blockages.
* Dirty Fuel Filter: A dirty filter prevents fuel from reaching the carburetor. Inspect and replace if necessary.
* Carburetor Issues: The carburetor may be clogged, have a bad float, or need adjustment. Clean the carburetor thoroughly, check the float level, and adjust the idle mixture screw.
* Fuel Pump Malfunction: A faulty fuel pump won't deliver fuel properly. Test the pump's operation.
Ignition System Issues:
* Spark Plug Problems: A fouled or worn-out spark plug can prevent ignition. Clean or replace the plug.
* Loose or Damaged Spark Plug Wire: A loose connection or a damaged wire can interrupt the spark. Inspect the wire and connections.
* Ignition Coil Failure: A malfunctioning ignition coil won't produce the necessary spark. Test the coil with a spark tester.
* Ignition Module Failure: The ignition module controls the timing and spark. This is less common but worth checking if other components are good.
Other Possible Causes:
* Air Intake Restriction: A clogged air filter or blockage in the intake manifold can prevent proper air flow, causing the engine to stall.
* Governor Problems: The governor regulates engine speed. A faulty governor can cause the engine to stop unexpectedly.
* Low Oil Level: Some engines have low oil shut-off mechanisms to protect the engine. Check the oil level and add oil if necessary.
* Valve Problems: A sticking or damaged valve can cause the engine to misfire or stall. This is less common but worth considering if other issues are ruled out.
Troubleshooting Steps:
1. Check for Basic Issues: Start with the easiest things: Ensure there's enough fuel, the fuel is fresh, and the air filter is clean.
2. Inspect Spark Plug: Check the spark plug for fouling or wear.
3. Test for Spark: Use a spark tester to verify a good spark from the spark plug.
4. Check Fuel System: Inspect the fuel line for blockages and the filter for dirt.
5. Clean the Carburetor: Thoroughly clean the carburetor and ensure the float level is correct.
6. Check the Governor: Ensure the governor linkage is free and operating properly.
7. Verify Oil Level: Make sure the oil level is sufficient.
Important Note: If you're uncomfortable with any of these steps, consult a qualified mechanic. Improperly working with the engine's fuel or electrical systems can be dangerous.
