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Gearbox bearing

Hey fellas, I have stripped the gearbox on my WD M20 to replace gaskets which were leaking.

The main shaft bearing at the clutch end, is of a double seal type. Who ever last replaced this bearing left both of the seals intact on the bearing. I was of the understanding that the seal facing the inside of the gearbox should be removed?

The bearing itself appears serviceable and the gearbox worked very well with no noises prior to disassembly so I plan to reinstall this bearing as I am not doing a resto on the bike.

Should I leave both seals on the bearing or remove the inner one?



Re: Gearbox bearing

I was advised by a friend, who was the chief development engineer at RHP bearings before he retired, to remove the inner seal...

He said the oil serves to cool as well as lubricate the bearing in that application...

I imagine he knows what he's talking about so have always followed that advice...Of course it may also work the other way with both seals intact!...Ian

Re: Gearbox bearing

In theory probably correct but I feel a lot more heat goes through the outer race in intimate contact with the aluminium case.
Sealed bearings run a a lot higher speeds than the mainshaft ever will and give long service.
IMHO keeping crud out of the bearing is a lot more important than washing away a little heat.
Never had a bearing fail from too much heat but have seen a lot collapse from crud being ground into or hammered onto a race.

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Re: Gearbox bearing

A number of modern gearboxes on cars and bikes use sealed bearings. It was found to keep crud out of the bearing.

Re: Gearbox bearing

Well Guys, after over thirty years in the bearing sales business, 27 with my own Company, I would wholeheartedly agree with Ian.
The benefits of running in oil far outreach the extra seal keeping out the crud. If there was so much contamination in the oil, the bearing would be the least of your worries.
Heat dissipation, less braking force from the grease, and far less friction from the oil lubricated unit would certainly extend the life of the bearing.
I would always take out the inner seal, but its your baby, your money and you pays the price, you makes the choice.
Good luck

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Re: Gearbox bearing

I always think that if you leave both sealings in your gear box, the bearing over time will fill with oil. Especialy if the bike is on a side stand.
Once the bike is started, the oil cant't get out, putting the bearing under pressure. I think thats a risk, isn't it ?

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