A cylinder port map out of a Nsr250 mc16 model. Timings are very racy and quite similar to early Rs125 nf4 cylinders but port lengths are narrower. This cylinder will seriously benefit from slightly bigger transfer timings while keeping the exhaust port as it is.
Total length of the cylinder is 86.3mm and it's a straight swap to all Nsr250 crankcases. Water jackets could have been bigger so upgrading your cooling system would be a good idea.
I really like the straight roofs of the exhaust ports...
*Numbers are in mm increments.