So, it's an mc18 frame with a gull arm attached.

It's got mc18 barrels, mc18 carbs.

A dry clutch can easily be fitted to any NSR engine, wheather you can externally tell mc18 from mc21/mc28 cases I dont know, though I'd guess you can.
If you take it to bits you'll soon find out anyway, if the centre crank seal is part of the centre main bearing, it's an mc18.

Offically none of the cranks are rebuildable, in reality if you can get the bearings they can all be done.
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