"Within spec". It's a phrase that makes me cringe. It's the same as saying, "Within service limits." But both are misused. While measuring the part or its fit is essential to gauging its continued usefulness, there is a lot more to parts inspection than that. And a really thorough inspection--not just making measurements--is a critical part of an engine rebuild.

One of the ways to discover much about both cylinder and piston ring wear is to measure the rings' end gaps. But beware. You can have a ring whose end gap is well "within service limits", but then you flip it over and find that its bottom surface is noticeably worn. The ring has a step worn into it where it rides on the bottom of its groove (the "land" in mechanics' speak). That ring should not be reused, no matter how "within spec" its end gap is. And this kind of ring wear is not unusual.

Another thing I often see is cylinders that are within Honda's extremely wide service limits, yet their clearance to the piston is three times the factory assembled specification. This is not a good thing, not something to be ignored, and some Honda cylinders get this worn before 10,000 miles.

Don't view "service limits" as a pass. Rather, think of them as extreme use, as if the bike were in the African Congo where no opportunity to rebuild exists. The bike can still be run that way. But it's not ideal when most of the engine's internal clearances are several times their original specification. "Within spec" often means completely worn out.