I am going to assume that you are not the original owner of this bike?
Do the marks look old? New? Was that the kind of noise you heard? The ring is okay? Reed valves okay? Sounds to me like something went through your engine, you need to find out a) when b) what, and c) why.
Anything in the intake tract is a suspect, plus any hard parts that are in communication with the crankcase. You say the piston, and wrist bearing are okay. If the ring is still good(no part of it missing) you need to start suspecting the big end rod bearing and the crank bearings.