A bad head gasket will usually show up in a compression test. A shorted spark plug will show up by switching the plugs. If the non running cylinder follows the plug, try a new plug. If it doesn’t, look for a bent or broken reed valve, or bad manifold gasket. Sometimes a crack in the ignition wires insolation will show up when the wire is plugged into the spark plug, but pulled away from the spot where in was shorting when moved to the spark tester. Make sure the insulting sleave on the magneto stop switch wire is in place as these can short to the motor cover in certain throttle positions causing intermittent problems. . . . . ❓
