Yesterday, after breaking in my motor, I was riding around my front yard. All of a sudden my motor bogged and died. I started to kick it over, there was no compression! The circlip fell out and put a bunch of pits in my piston and head, and a deep scratch in my cylinder. So... if any of you guys are rebuilding something, DOUBLE CHECK EVERYTHING!!!!!!!!!!!!!!!!!

P.S. Can my head be reused, or will I need a new one since the "pits" are in the chamber?

 

I did EXACTLY the same thing once. Stock 86 cylinder on 8th bore. Cylinder was bored to 10th and saved. Piston was junk, tossed it. Head was OK, just a little cleanup on it. If it's pitted too bad, you may want to get another as those pits will let carbon buildup in them and create misfire problems.
When you install circlips, install one side with piston out, make sure it's in right. Then, put piston on, etc.. . make sure that clip is in solid and can be turned in it's groove. Don't leave the "cut" ends in the notch for removal.