and swap them with the plastic weightplaceholder rings of a starlite
I also want to do this. I have a broken north and I want to transfer the rings to a Onestar.
Like most plastics with a weight ring it appears to be a press fit. If you put the tip of a screwdriver under one side and rest the shaft on the other side you should be able to pry it out bit by bit, working around the rim.
if your northstar is already broken, it shouldn’t be very difficult to get the rings off if you don’t mind breaking it further.
I think the real trouble is getting it off without breaking the yoyo.
Try hooking something on the ring and just pulling.