What's up with this piston?

[83cb650sc]

Hey guys, I'm in the process of tearing my engine down; took off the #1 piston to clean it up (all 4 have apretty good layer of carbon buildup), and after I got the carbon cleaned off the top I found what's in the picture. Both sides of the piston between the valve reliefs and the edge are like this.

I also found something similar looking on the sides at the ring lands. The third pic is the skirt area, wondering what the opinion is on that (been a while since i did anything with engine internals, and then it wasn't much).

 

[DrJ]

The skirt scoring is normal, the other stuff I'm not certain.

 

[surffly]

Took the engine apart to clean? Really?
And didn't figure on doing pistons and such while you where there?

I would assume at some point the motor was slightly rusty on the inside from sitting for years.
Looks like corrosion pitting on the pistons.

I would replace and over bore.

But assume many will chime in saying "re ring and put it back together"
Prob will be fine for the amount of riding it will see.

 

[83cb650sc]

No, I did not tear down my engine to clean it. Tore it down because it needs new valve stem seals and a few other gaskets, and figured I would go ahead and take the opportunity to give everything a good looking at. Cleaning off the piston was just to inspect it for anything odd (like crater-looking spots on it). Went into the teardown expecting to replace pistons.

As far as the corrosion idea, maybe on the sides, but the places on the top don't look like corrosion pits to me...

ETA: As for how much riding it sees, it's a 1983 model, I've owned it for the past 2 years and put around 10k miles on it (rode it a lot, just didn't have very far to go very often). Can't speak towards the riding habits it was subjected to for the rest of its life.