What would cause the spark plug in lawn mower to keep burning out?

1. Incorrect Spark Plug: Make sure the spark plug you are using is the correct type and size specified by the lawn mower manufacturer. An incorrect spark plug can cause overheating and premature burnout.

2. Faulty Ignition Coil: A faulty ignition coil can provide insufficient voltage or an irregular spark, leading to spark plug burnout. Check the ignition coil for any damage or corrosion and replace if necessary.

3. Lean Fuel Mixture: A lean fuel mixture (too much air, not enough fuel) can cause the engine to run hot, which can lead to spark plug burnout. Ensure the carburetor is properly adjusted, the air filter is clean, and there are no fuel restrictions.

4. Overheating: Excessive heat can cause spark plugs to burn out prematurely. Check for proper airflow around the engine and ensure the cooling fins are clean and unobstructed. Clean or replace the air filter if it's dirty.

5. Worn Piston Rings: Worn piston rings can lead to excessive combustion chamber pressure, causing the spark plug to overheat and burn out. Check the piston rings for wear and replace if needed.

6. Faulty Spark Plug Wires: Worn, damaged, or loose spark plug wires can cause poor electrical connection, leading to spark plug failure. Ensure the spark plug wires are in good condition and properly connected.

7. Magneto Problems: If the engine is not generating a spark, the magneto may be the culprit. Check the magneto's flywheel key for wear or damage, clean or replace the magneto's points if needed, check for faulty wiring, and check for a worn armature.

8. Excessive Carbon Buildup: Carbon deposits on the spark plug can make it difficult for a spark to jump the gap, causing the spark plug to overheat and fail. Clean or replace the spark plug and check for potential sources of carbon buildup, such as a clogged air filter or rich fuel mixture.

Remember that if the spark plug keeps burning out despite addressing these issues, there might be an underlying problem with the engine or its components. Consult a lawn mower repair manual or seek professional assistance for further troubleshooting.