Spark plug not wanting to stay put problem

[Supa Ninja]

Thanks for the reply's. I swapped the head and discovered the shim/gasket between the head and cylinder head was missing a section. It had a bit of a lawn mower sound so that was probally it. It also probally sucked outside air durning the intake stroke causing it to run lean, the plug probally got to hot and the the threads failed on the head.
I managed to lose one of the bolts for the throttle body and the hardware were closed when I made the discovery so I'll update this thread tomorrow when I get it running. Once again thanks.

Nick