Hi there has anyone ever seen an nsr crankshaft with an aliuminium centre bearing it came to me in a knackered 21 motor,one of the big ends has let go, the odd thing is the rod that let go is an nx5 conrod i have rebuilt the motor with a rebuilt crank i had in stock,just wondering if youve ever seen a crank like it,jonmac








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John

Looks very interesting.

If you are pretty sure that the center part is made out of aluminum, then it is not a bearing but a labyrinth seal.
This is common on Yamaha cranks and I can't see why it shouldn't work on a nsr crank as well.

Very nice find, I never had surprises of that kind while splitting crankcases.
Please, post some more pics.
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2t-racelab.com

I was going to say the same and suggest it was a labyrinth seal . I have an old racer friend that makes them and uses them on his old tz's etc .

On the yam's they have a bearing either side of them... If its a labyrinth seal then the crank has been running on 2 bearings with no centre support.. no wonder its knackered....

Hi Nobby,the crank itself isnt knackered,the centre bearing has galleries in it for lubrication and it spins over as a bearing should,the ali bearing has a locator peg also,could it have a steel race in the ali ? it is definatly smooth to turn,would a labrynth seal have these characteristics ? the only way to find out i spose is to dismantle it and have a nose inside,the big end retired on the nx5 rod the rest of it seems fine,thanks,jonmac.
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John

John, It would be interesting to see what it is / does..... It could be the answer to our impending doom re the shortage of koyo centre bearings. Surely it can't just be a yamaha style labyrinth seal..... Keep us posted please.