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MC16 port layout

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. 


  1. I'm not sure I understand your question.
    How come deck height is relevant to this port layout?

  2. Deck height is distance from TDC of piston to top of cylinder block.
    Obviously, if deck is non zero you have to subtract those extra mm's to find the real timings..
    In cases, there's even 'negative' deck -piston above cylinder-, which would also affect timing measurements.

  3. This is a port layout not a port map hence it does NOT include any timings... I haven't included rod length, gaskets thickness, stroke etc. etc. so I can't see how deck height can be of any use.

  4. You included the distances from the port floors to the top line, which seems to be the barrel's surface. If that's not used for timing measurements in a port laypout, then what is ? You can as well erase them.
    Anyway... Cheers.


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