Re: Compression test follow up
Without actually holding and looking at the pistons, and bores I can only offer guesses and more questions.
Are you saying both #3, and #4 look like the picture??
With what little I can see in the picture---
it looks like the oil ring is stuck
top compression ring has a "burn" spot on it, also it looks like similar marks in the same spot where the ring land has been rubbing the bore --are there marks in the bore too? ---next I would look at the skirt wear to see if it looks like the rod is bent(skirt wearing at the top on 1 side, on the opposite side at the bottom)
the marks on the ring land between #2 ring and the oil ring seem to be some sort of debris moving and pounding on the land ---it is not from touching the bore directly because there are no up and down marks
Before you replace pistons you need to have the bore measured carefully ---in many spots.