- Incorrect engine timing: The ignition timing may be too advanced or too retarded, which can cause the engine to run rough and stall.
- Air leaks in the intake system: Air leaks can lean out the fuel mixture, causing the engine to run lean and stall.
- Fuel restriction: A clogged fuel filter, dirty carburetor, or kinked fuel line can restrict the flow of fuel to the engine, causing it to run lean and stall.
- Faulty spark plug or ignition coil: A worn or fouled spark plug or a weak ignition coil can cause the engine to misfire and stall.
Troubleshooting steps:
- Check the engine timing.
1. Remove the spark plug.
2. Insert a long, thin object (such as a piece of wire) into the spark plug hole until it reaches the piston.
3. While holding the wire, turn the crankshaft slowly until the piston is at the top of its stroke.
4. Check the alignment marks on the flywheel and the engine case. If the marks do not align, adjust the timing according to the manufacturer's specifications.
- Check for air leaks in the intake system.
1. Spray starting fluid around the intake manifold, carburetor, and other potential air leak points.
2. If the engine RPMs increase when you spray starting fluid around a particular area, that area is likely the source of the air leak.
3. Repair the air leak.
- Check for fuel restriction.
1. Disconnect the fuel line from the carburetor.
2. Turn on the fuel petcock.
3. If fuel does not flow out of the fuel line, the fuel filter or fuel line may be clogged.
4. Clean the fuel filter and fuel line or replace them if necessary.
5. Reconnect the fuel line to the carburetor.
- Check the spark plug and ignition coil.
1. Remove the spark plug.
2. Check the condition of the spark plug. The spark plug should be clean and have a sharp electrode. If the spark plug is worn or fouled, replace it.
3. Test the ignition coil. Disconnect the ignition coil wire from the spark plug. Hold the ignition coil wire close to the engine block. While kicking the engine over, look for a spark. If there is no spark, replace the ignition coil.
If you have checked all of these things and the engine is still not idling properly, you may need to take it to a qualified mechanic for further diagnosis.
