Well if you're talking about the pin that goes in the piston, I guess that starts out at 4mm exactly, I just replaced one that measured 3.92.. then I guess if you're talking about the hole in the top of the conrod, I guess that starts out at 4mm to match.. so if it's more than what you think is safe out of spec, I'd get rid of that.. then if you're talking about the crank pin, that starts out at 5mm and also the con rod big hole is at 5mm, so if your crank pin is less than 4.91 Rayaracing told me that was "borderline" towards there being any point in fitting a new conrod.

As for the actual conrods, when they enlarge they don't seem to enlarge as fast as the crank pin or wrist pin, when I replace them they'll be like 5.04mm in the bottom hole for example.. I had one measure 5.09mm but that was extremely high mileage.