Honda Crankshaft Differences
Honda only has one part number for the crankshaft from the PA50I and PA50II, but the crankshafts are different as they have different endings. The bushings that ride on the crankshaft are also different. Their inside and outside diameter are different, meaning the drive faces will only fit on the same crankshaft. Here is a picture of them side by side:
The PA50II crank is on the left. It is possible that the change was made to put a roller bearing (in the clutch bell) with larger roller pins - to take higher load.