I would strongly advise for the time being to use R cylinders with R heads, or SP cylinders with SP heads. Don't mix anything up! (I.e. don't even run one side R-spec and the other side SP-spec.)

Either spec, well set up and maintained will give 61~63hp on a stock NSR.

Once you have a good base to work from, then you can be confident to modify.

As Fontyyy already mentioned, differences in port heights are generally just down to manufacturing tolerances. It doesn't hurt in the least to clean up the nikasil on each port window so they all match!

Finally, R and SP barrels are different heights, and R and SP heads have different combustion chamber volumes. Make sure you have the correct combination of parts. It doesn't matter what bottom-end it's all fitted to, what PGM-III you run, or what set of carbs you are using... that stuff is all interchangeable with no measurable differences in power.
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Andy.
NSR-WORLD.COM

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