x3 on being lean.....the ignition problem and the kill switch and plug caps are not the problem...they only kill the spark going to the piston itself.. However if your running super lean you can create a "dieseling" effect.....basically something in there is either SO hot or detonating so badly that it is continuing to generate enough heat inside the cylinder to continue igniting the fuel.. like fastbanshee said....DO NOT ride it or start it til you can track down the problem or you will definately make things worse...
let us know what you find and we can help you out with your problems...