I'm sure Matt will know how to do it...

Why would I even consider putting NSR barrels on an RS

SACRILEGE

If you did want to put NSR barrels on I suppose you could use old CR125 or RM125 pistons. Up to '87 used a 54mm bore & 14mm pin I believe on both models. Obviously deck heights and piston lengths etc etc would need checking and adjusting but it could be done.

That's all I'm gonna say on this subject.