Annoyed at finding this cylinder with low compression, I ripped the motor back apart to find there was a ridge left in the bore that was noticeable on 30 percent of the bore centered in the compression area. I suspect the machine shop broke his tooling mid way through the bore and it shifted the block a few thousands to the side and it didn't line back up perfectly centered to complete the bore. Like I said it was a small ridge that was maybe 2 inches long an maybe 0-5 thousands at its highest point. I suspect the rings during the compression direction would fall off this Ridge and breed some pressure off. I'm glad I opened it back up as I may have caught a ring on it and broke it. an hour or so of hand sanding and new mostly dry hone removed the ridge and produced a nice smooth bore. The subsequent compression test bumped up to 130 but has continued to improve as the rings are breaking in on muffs. Maiden voyage on the lake yesterday and it ran really well! I will check compression again after a few more gallons of fuel are run through it.
