Here is what the Honda PA50II book says:
Standard end gap, both rings: 0.15-0.35mm or
0.0059-0.0138in.
It says if the end gap exceeds 0.6mm or 0.0236in they need to be changed.
When measuring them it is always best to use the bottom of the bore. The pop, where all the heat is, wears more than the bottom. If you set the end gap at the top too small there is the possibility that they can bind at the bottom