Plug burning out after shutting down

[hellofacopter]

Just replaced the piston and ring in my Hyper 50. Going thru break-in procedure and after I shutdown the engine I couldn't start it again. The engine was idling perfectly when I killed the throttle. Went to start back up and it wouldn't start. Checked the plug and its burned out.

What would cause the plug to burn out after killing the engine?? Ran to hot? To rich?

[JimLerch]

Too Lean, too hot, or a bad plug.. The plug probably broke in flight. The coil only needs to conduct electricity while starting with the glow wand. Once the engine is running, the coil can break in the center, but it will continue to glow and keep the motor running.