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That looks like it may be stock size with overbore.l And stock compression. It's only the last few years you could get big bore pistons with stock compression, unless you custom ordered.
I have same pistons. 67.5 mm bores, 901.7cc or 900cc which is the normal saying and written inside the pistons.When those bores are worn, not possible to bore a little bit more for next size since the sleeves are of the type that will fit case without machining (or just a little grinding).You need to measure at the skirt 1/2" up from bottom under wrist pins. Not top where all pistons are slimmer.
Yes, pistons are oval, your top pic show the correct place to measure. Your measurement verify 67.5mm and 900cc as printed inside pistons.Bore diameter - piston diameter at the skirt is the clearance. Cast pistons have usually smaller clearance than forged.
Hey PeWe, you're saying that going from my 67 HA to 68mm is not going to be possible without re-sleeving? I may need to do this as 1 of 4 liners is showing vertical scratching above and beyond normal break-in wear.