The timing chain coming off allowed the cam to be in the wrong spot at the wrong time, allowing the piston to hit the open valves. If you see slivers of metal in the oil now you chould check to see if there is an oil filter in the bike. I bet it has some sort of centrifugal oil filter/screen that traps the big stuff, at least an XR200 does. The other guy is right, www.servicehonda.com
has cheap parts. Is your girlfriend mad at you?