Hi Al
The pistons actually look quite good, much better than mine were anyway. My guess would be that they have not done a huge amount of mileage.
It's difficult to tell from your pics the condition of the bores but, again, they look ok.
Carefully remove the rings (making sure you remeber which pistons they came from and remeber there is a top and bottom ring. Do a gap test in the bore (see the workshop section on this site) and if the clearance is within spec then refit, or replace with new.
Make sure that piston ring grooves are completely free from crap.

I'm not an NSR expert (might be when I've finished building mine) but this is just common two stroke knowledge.

Good luck.

Mike
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