Oil leak sump/bell housing part 2!

Hello everyone,

I finally bit the bullet: stripped down my ‘82 850 T4 enough to crab the frame and remove the gearbox.

The input shaft seal was indeed leaking around the input shaft itself and had started to deposit oil through the starter ring and onto the clutch.

On removing the splined boss to get access to the seal, I noticed the former had two black lines on it from the lips of the seal.

I can’t feel a ridge with my nail so I’m wondering if friction has just discoloured the metal?

I’d probably replace the boss but i’s not manufactured anymore and Gutsibits solution is a new clutch kit new type of boss for £186!


The splines look perfect, so I’d try to reuse it!

Hi Mike,

Thanks for your message. Yes the splines all look good.

It’s the two black lines on the polished shaft which concern me - putting it back in with a new oil
Seal and ending up with a similar leak.

I’ve never used them, but these Speedi Sleeves came up in a recent conversation as a way of repairing a worn shaft.

Many thanks! I’ll take some measurements of the shaft.

I have a brand new unused one if that is of any interest.

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Just give the hub a gentle polish with a worn green scouring pad or even bit of metal polish/T-cut and see what it looks like, if you can’t currently even feel a groove it should all be good,
you can even install the new seal just slightly deeper, say 1 to 2mm and the seal lip will run on an unmarked section of the hub

Out of curiosity how many miles has that hub done, it looks almost new ?

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Many thanks Dave. Much appreciated.

Apologies for the late reply.

I have bitten the bullet, cleaned and replaced the hub! I’m hoping I womnt be pulling the bike apart again in a few days with the same leak!

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Many thanks for the photo and advice. I decided to take a chance and I did exactly as you said.

I cleaned and then polished by hand with Peek. The black marks which must have been accumulated seal material came away quite quickly.

Two lines were left by the seal lips but I really could not detect they were grooves or were worn.
They appeared to be polished to a brighter level than the rest of the shaft.

By accident rather than design, I did end up putting the seal in a little further than I found it. Thinking this might be an error, of course I could not budge it to move back out so I left it.

I think it pushed onto a “land” further into the casing. On reflection, I thought as you say: that the seal lips will be on a new face of the hub. Fingers crossed now!