[Jim Brierley]

That type of scratch usually means the wrist pin is moving out against the cylinder wall. I would remove that piston for inspection. I suspect the pin keepers are missing. This should be looked at before doing anything else as it could be disastrous. A proper fix would require either sleeving that cylinder or a complete re-bore, as without that you will have a lot of blow-by and some loss of compression in that cylinder. From the photos, I am not sure the weights are welded to the crank adequately, take a good look at that while you are at it.