I have a few nsr's and an ns400 and want to clarify the interchangeability of nsr crank's. I know there are differences in mc18 MK2, mc21 and mc28 but are they interchangeable? Different crankwebs, flywheel etc? What would be required to put a 28 crank in an r5k if it's possible? I have all these and an r2j which I understand is quite different, and just want to know the finer details of each. Thanx for any input/ links.

R2/4J MC18 - 96mm crank webs, center seal next to middle bearing.
R5K MC18 - 96mm crank webs, integrated center seal into middle bearing, same as 21/28.
MC21/28 - 100mm crank webs, integrated center seal into middle bearing.

R2/4J cranks can only be used in R2/4J casings.
R5K cranks can be used in R5K casings and MC21/28 but not advisable.
MC21/28 cranks can be used in MC21/28 casings only.

As for your question what you would need to put the 28 crank(100mm) into your R5K casings, you need MC21/28 casings as the crank webs is too wide for the R5K casings(96mm). You can still use the same flywheel and pickups.

Cheers
Mario

You can turn MC21 cranks down to fit R5/6K crank cases. See pictures on NSR-World's face book page of ours.
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If I have to take the carbs off once more...

Thanx guy's. That helps a lot.

StephenRC45 wrote:You can turn MC21 cranks down to fit R5/6K crank cases. See pictures on NSR-World's face book page of ours.

Correct, have done so myself, allot of work !