Dave (bigwave), you should read this http://www.nsr-world.com/rockoil/

You need a 100% fully synthetic 2 Stroke (2T) oil for the engine, delivered by oil injector in your case (rather than premixing with fuel in tank). The top spec fully synthetic 2T injector oils from leading lube manufacturers such as Castrol, Rock Oil, Fuchs Silkolene, Motul, Shell etc is what you need.

Make sure you don't use synthetic 2T scooter oil or semi synthetic 2T oils.

2 stroke engines are completely separated from the transmission, with respect to oil. Unlike 4 stroke engines where the oil has to lubricate the engine & gearbox. So choose a dedicated 2 Stroke Motorcycle Gear Oil, again from one of the manufacturers above (or equivalent).

Wet or Dry clutch? Some racing 2T gear oils, designed for bikes with dry clutches, have enhanced high shear lubricating film additives (reduced friction under high load). As the gearbox oil does not touch the clutch, this is good. But if the clutch is Wet, the gearbox oil also lubricates the clutch plates. Such 'special race' gear oils can actually reduce friction so much they can cause the wet clutch plates to slip. To make it easy, most leading lube manufacturers make high end 'universal' motorcyle gearbox oils which are suitable for both wet & dry clutches.

Don't mess around looking for a 4 Stroke (4T) synthetic engine oil for your NSR gearbox.
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30