Piston damage

[vtscorp]

I've been having trouble getting a 77 sting 440 to run well. Today I decided to pull the heads off and see how the pistons we're looking and it wasn't good. The PTO side which I expected to be the problem looks great but the recoil side has a hundred round holes like someone threw a handful of bbs in there.

Has anyone seen this? What could have caused it? The cylinder walls seen fine so I guess I'll get a gasket kit and a new piston and keep trying.

[stinger440]

Can you post a pic? Sounds like that cylinder sucked something In and it bounced around on top of the piston till it shot out the exhaust. Is the electrode still on the spark plug? Are the rings intact?

[vtscorp]

The spark plug is intact. The holes are perfectly round so it would have had to be a hardened ball bearing. Do the Cuyuna 440s have bearings in the lower end? It all seems to be moving smoothly. I thought if a bearing shredded it would be clunky. Could a shredded bearing make it up into the cylinder?

I guess I'll find out once I tear it apart.