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I couldn't tell much by looking through the exhaust port, it was too small to see the side of the cylinder. I did notice that the parts saw 5100s had a bulge cast into the cylinder right above the flywheel which my saw didn't have so I guess the cylinders are a bit different. I cut a little bit of wood with my saw this morning and decided not to do anything with it. It runs so well that I don't think it needs any improvements plus the saw I borrowed had a ruined piston so the cylinder could be bad also, mine looks like new..
Not sure if this was answered or not.
The open port cylinders have this mark on the cylinder. The PS-6400 which is open port is the same way vs. the 7300/7310 & 7900/7910.