Those scratches are not caused by foreign debris. Looks like seized piston probably due to a combination of tight engine and high RPM's while engine was cold and sleeve had not expanded.

[QUOTE=asw7576;11042560]This is brand new engine with dirty manifold and pipe.

It happened twice with the same manifold and pipe ( 3 years I never clean the inside, ie. dirty )

The engine quit working after just few laps. I check the engine exhaust port and notice big scratches on the exhaust port.

I suspect the turbo charge effect ( or sonic pulse created from the pipe's cone ) is pulsing back some carbon dirts from manifold into combustion chamber.