Yes Dave, I do in fact dispute this.

The Suzuki and Aprilia 250's have a labyrinth seal, but the NSR has a simple rubber seal. Fact!

This rubber seal is also a good way to tell if a centre seal's shot. What I do is to spin the centre bearing (crank on the bench, not in the bike of course), and if it spins freely then there's a good chance it's worn out. I then sit the crank in the vice, pointing skyward, and carefully spray WD40 into the bearing through the oiling holes, just up to the level of the holes, and see if it leaks out through the seal. Only one side of the bearing is sealed and as I haven't got a crank right here in front of me I'm not going to say which side it is now.

That's how you can do an easy quick check anyway.

A good crank will have a 'stiff' centre bearing because it'll be tight on the rubber seal.