How was my engine running? (with pics)

Good day everyone,

I had posted a while back asking about possible and recommended upgrades for my bottom end. Since then I haven't had the time to start but I have an idea of where to go. However before I dismantle the crank for cleaning can anyone tell me what these scoring marks on the left piston were from? the scoring marks are on the intake and exhaust side. There is no wear on the main bearings or the piston. It's solid. This was bike is an unknown variable for me I purchased it as a barn find with no idea of mileage.

Looks like a minor seizure to me (If there is such a thing), rather than catastrophic.

I would have thought the same thing except the engine was turning over just fine. The opposite piston had broken rings. Could it have been a leaned out left bank?

383wss said:

I would have thought the same thing except the engine was turning over just fine. The opposite piston had broken rings. Could it have been a leaned out left bank?

Click to expand...

Well several years ago I rebuilt my engine with .020" over and a cold clearance of only .0035". It ran fine for about 1000mi until a hard end of season ride up a through an even colder pass caused it to seize hard not once but twice. Both times after cooling it would start and run pretty good but when I got home the engine was definitely louder but still not really smoking. No broken rings but both pistons were a lot worse looking than your example.

Oil change neglect.