Was mowing yesterday as the grass was too high for ZT mulcher. I heard a rattle when I got into some taller grass and a couple rounds later the tractor stopped. Raised the hood and the spark plug was laying on top of the engine. It stripped the threads out oh the head. I put the plug back in just to get it to shed. Now need to get a helicoil to put in it. My ZT does not like tall grass.