its sounds like it has seized up on you im afraid mate did it slow down quite fast maybe even lock the rear wheel for a moment?if so then it has seized yoou need to find the reason why before you rebuild it ..ie is there plenty of 2 stroke oil in it?does the oil pump work ?is there air in the pump?these are the main reasons for it happening,i bet you were giving it some stick when it did it or just before it did it?let me know and i will try to help more ok ,adam
adam bike doctor, July 2006