Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Have you ran a cylinder balance test? Loosen the spark plug wires, and with the engine idling, remove one wire at a time. Engine should continue to run. If engine dies, when wire is removed, the opposite cylinder is not firing.
I f you find the cylinder not firing, then check it for spark, and compression, if both are good, check the valve movement. No spark, likley the coil on that cylinder is bad.