What caused this?

[riding4fun]

This happened a couple weeks ago during a race. Not sure why. The plug looks black. What do you think?
There is some scratches in the cylinder that are centralized, other than that it looks good. Ring is still in it but does not move and is closed as if it was in the cylinder. Both circlips are still intact.
It's a 2004 CR85 motor.










Thanks,
Darrell

[o4twinpeaks]

I would split the cases just to check if something came loose. Was thinking part of the cage off the bearing but how could it make it out of the rod? Screw from the reeds? Not sure what kind you are running. Electrode off plug? There was definitely something foreign and hard in there. Any jb weld in the cases?

These are just thoughts

[witech]

Did the ring locating pin come out and pound the heck out of the chamber?

[mini racer #39]

that is a roller out of one of your berrings

[riding4fun]

Originally posted by mini racer #39
that is a roller out of one of your berrings

After doing some research that's what I'm afraid it is. Time to split the cases.