Uh oh.

May be another problem. I've just poured oil into the left crankcase to flush the crap out, and some has leaked accross to the right - I think. With the engine upside down is the gearbox oil likely to leak out of the crankcase?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Ok, update and education, so listen up if yer interested!

The NSR crank has a labyrinth seal between the two sides, not a rubber seal. The cuts down on friction, whilst still performing admirably as a block to air. This explains why the oil will leak accross fom one side to the other. There is a slight air leak, but since the pressure down there is so low (about 5psi above ambient) it's not significant.

The O ring (as supplied by Andy) fits around the centre bearing, but the seal through the bearing itself is the labyrinth.

This came from Elliots, the grey bike importers, so I'm pretty sure it's true.

Anyone dispute this before I rebuild my engine? Matt?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

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.

Oh bugger.

The bloke did quote the RGV at the time. I must admit I wasn't sure, but he insisted that was the case. Sigh. Why do people make stuff up?

So, is my crank seal shot if oil leaks accross from the left to the right or not? I'm getting fed up of this already.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

In theory yes. However, I've taken cranks out of perfectly good running motors only to find that when I do my WD test it very slowly seeps out.

It could be that when up to running temp the seal softens up and the spring tension helps seal it.

I've also performed the test that you mention, about filling one case with fuel/oil and seeing if it leaks, and I've seen a couple that will weep a little of the mixture over time, but again, once running they work fine.

Just goes to show that up to a point, the good old NSR is self healing......maybe!!

I've also seen bad running engines with a centre bearing that spins without any drag and leaks like a sieve. Throw in a new crank and you're ready to rock.

Thanks Matt.

The motor was running perfectly before the coolant problem, and the crank feels good to turn by hand.

I'll rebuild and sod the seal!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball