r100gs - gear oil just won't stop leaking. WHY?
 

Hello all, I've a r100gs 1988 model and I have a bit of a problem.

The bearings went on my last gearbox and unable to replace them myself I opted to get a new (well reconditioned) box. I fitted this and started to notice oil coming from the output seal. It was coming out at the rate of about 100cc every 500miles. Not a lot but enough to cause a lot of mess on the exhaust box. As we plan to go to Africa it needed fixing as gear oil is harder to come by there to keep it topped up.

I, and everyone who saw the oil coming out, was certain that the seal was leaking. I got in touch with the shop who sold me the reconditioned box and they agreed to send me a new one to try out. I have put that in and the oil is still leaking out!

I'm now really confused. It can't be the output seal twice I am certain it is fine. I'm not overfilling the oil and I'm using the correct type. I'm not busting the seal when I attach the drive shaft. The V shaped groove in the back of the geabox is the newer type small diameter hole so I shoudn't need to fill it. What else can it be?

Any suggestions would be appreciated.

If you are using synthetic switch to Dino oil. It may just be an old type seal.

1) The gearbox is vented through a hole in the screw for speedometerwire (the main earth-connection is also attached here.). Remove the screw and see if the hole is blocked.


2) There is a small notch above the seal. On all paralever-models this has to be filled with silicon. It's a common mistake to "forget" this during a rebuild or when the seal get changed.

It's possible to check (and fix) this by loosen up the rubber-boot but it's much easier if you remove the wheel and shock and slide the swingarm 20mm backwards. You don't have to loosen the shaft.

3) The seal is mounted different on paralever and monolevers. On a paralever the spring should be facing towards the gearbox (you should not be able to see the spring).
This can be inspected at the same way as #2.

The orientation of the seal and using silicon in the notch is the only thing you have to change if you use a monolever box in a paralever.

Totaly agree with Ali Baba:thumbup1:


Werner

Thanks for suggestions so far.

I am using a semi synthetic oil. 80/90 so I'll try and switch to plain oil to see if that works. I think the seal may be the older type. Speedo drive and earth screw are clear of blockages. The seal is mounted the correct way around with the spring facing the oil.

Alibaba, I was under the impression that the notch in the gearbox casing needn't be siliconed if it is of the newer small type. The last box I had required the silicon filling as it has a larger V shaped groove in it and then I drilled through a 1mm hole so that it could still breath out of this. This box has the newer smaller notch already and I thought the problem of oil leaking out had been corrected by the manufacturer so I didn't have to silicon this one. The notch is a lot smaller. You think it still needs doing? And you do still think I need to drill a hole back through it so that it can breath?

Thanks again

The notch should always be completely filled (on a paralever).
All components have separated vents. The gearbox vents through the earlier mentioned bolt, bevel-box through the plastic-vent and the cardan-housing through the pivot bolts that attach it to the frame.

I have a bike with a late gearbox (1996) and when the notch was open it used 100 ml oil every 1000-2000 km. It's worse at high speed and mountain-passes.

Alibaba is as always on top of this :thumbup1:

Yes - known BMW "personality"... or -fault-... depending on point of view.

You need to fill the hole with silicon.

I use Omega 690 80W/90.
www.smortknik.se
Magna Industrial Co. Limited
http://www.magnagroup.com/products/o...re/odis690.pdf

Surpriced that the shop that supplied the gearboxes to you did not know this... You -did- point out to them that you were replacing a GS/PD gearbox, right???...

Once sealed - no problem :mchappy:

Thanks guys, will seal the hole. Do you think there is any way of doing it without removing the driveshaft?

Yes (read my first post).
It's even possible to do it with the swingarm in the frame but you will have a hard time to get the boot back on.

I Had a problem with oil leaking out of the "V" groove on the output seal casing had two atemps of trying it fill it with siconce but that did,nt work, when l changed the seal the third time l filled the groove with JB weld and sanded it with fine grade wet and dry to make a good finish, 10,000 miles later and i,ve had no leaks.

just out of interest, did you get the box from sherlocks?