I'm noting this here so I don't lose it. I'm told that there were three different pistons for CB/CL72s in three different compression ratios, I'll have to find part numbers and ratios.
The point is that those 250cc bikes use the same or close to the same bore and stroke as these 250cc bikes, but their combustion chambers were much deeper to keep compression low. I'll attach photos.
Why do I care? I've been researching Terry's use of CB77 pistons in his stock bore K0, this would appear to be a scaled down version of that modification (117cc/cyl vs 184cc/cyl) nobody's ever done it before, I've got a spare 250NH engine to experiment with and I'm curious if it can be done. It might not add much power, but this little twin already revs to 10K and has 9.2:1 compression, bumping it up to 10.2 might make 15-20% more useable power.