The first time I saw the failure was as I pulled into a parking lot and the bike died. Eventually I was able to get it restarted and it seemingly ran fine after that. Looking back, I wonder if this is when it dropped the tang on the center spark plug and began running on only one plug in the front cylinder. I did notice it was a little more rough after that.
Here is a picture of the spark plugs. The one with the broken tang came from the center hole in the head. The other plug came from the offset hole.
After tearing down the bike to see where the broken tang went this is what was found. I wonder if the tang first lodged then hit the head, causing the indent, then slipped down the side and caused the damage to the rings and lands on the piston. Once broken, the piston allowed burning gas down the cylinder which caused oil starvation and scarring.
Small indentation on Cylinder Head (right center):
The mechanic seems to think it was pre-ignition that caused the broken rings and lands. If that's the case the problem may be outside the cylinder. It also means the other cylinder will need to be torn down to see if there is any damage there. It also means that a "crate" engine, which is what the shop is pushing for, may not solve the problem. I hope at least for a crate engine. If I'm right, the lower end will need to be pulled apart to see if there is any additional material left in the bottom of the motor, which will probably be necessary in either case anyway.
Cylinder Wall Scouring:
More scouring on cylinder wall, opposite the scouring above:
Broke ring lands, scraper ring was also broken:
I really hope my buddy Jim is wrong about this bike being abused and hope that this is just a freak occurrence. If it was abused, there may be other unknown damage that is waiting to crop up.
More to come as we hear more about what damage exists and what course of action KTM takes to resolve this. Hopefully, no ones else's MTC Failure has the same result as my case.