Title says it all really.  I topped up my transmission with gear oil and used the special tool for measuring the level and put it exactly up to the line and went for a drive.  Suddenly gear oil is leaking from the top of the transmission and on to the exhaust.  What went wrong??

I know I didn't overfill (at least I didn't add any more than prescribed by the little measuring tool) and have changed the oil over the years without this issue.

ps.  1985 k100RS

There is most likely a split in the rubber boot around the clutch pushrod at the back of the gearbox.
BMW Part No.  23 13 1 338 731   It is accessible without removal of the swingarm but is a bit fiddly to get on.

As Rick says. However, before cursing the fact that you don't have four hands, gently try the clutch arm pivot to see if it will come out. If it will, then you might want to try the following:-

Unbolt the exhaust silencer from the footpeg hanger - don't take the system off!!
Hang enough weight off the back end to open up a big enough gap to slide the clutch arm pivot out (it took 21 lbs last time I did it!)
Slide the pivot out, drop the clutch arm off and remove the old boot
Keep the worm drive (unless you've got a new one)!!!
This is the damn awkward bit and you'll need to get under the bike...
Slide the pivot back in so that it's hanging in the gearbox casting
Put the boot and spring on the back of the clutch arm, reattach the clutch cable and hold the assembly up to the gearbox with one hand
Slide the pivot back into the clutch arm with the other - chances are it's just out of reach so I used a mallet

If you get this far, you've beaten the job.

You say the top of the transmission.  Is the gear oil puddling around the breather?

I've seen before on some forum where someone topped up their transmission after improperly using the measuring tool.  The tool should be inserted all the way down to the bend on the tool.  If you just stick it in until it seems to stop you may not have inserted it far enough.  In my experience with over 400k miles of owning BMW bikes the transmission does not need to to topped off ever.

The only times I had to top mine up was when the clutch boot was leaking. If it isn't leaking then you shouldn't be losing any. Although.......when I was doing the recent rear seal job my drive shaft was very well oiled from somewhere.......

Little question too...no chance you used a power washer up the rear and got water in the transmission? In which case drain and change the oil and see what happens.

WELL, if it's supposed to be inserted to the bend of the tool then I have put way too much oil in the transmission.  I wasn't able to insert the tool very far so that could be the problem.  Not sure how it's supposed to go all the way to the bend though.  Anyway, I'll drain out the fluid and put back exactly 850cc and see if I have leaks.

When inserting the measuring tool if it stops before the bend in the handle is against the filler hole you need to wiggle it to get past what it is hung up on.  You may also need to raise and reinsert it.

Thanks so much Kiollt!  That solved the issue.  I drained out the transmission and there was too much oil.  I wasn't measuring correctly.  All it took was a year to forget how to do that little job.  duh.

Now that you know how far the measuring tool should be inserted where you able to insert it the full way?  Just want to know.

yes.  I had already drain the transmission and then poured in 850cc and it measured just right.  Thanks for rattling my brain.

Great to hear that it was nothing more than a "miscalculation" and the honest admission of the mistake is refreshing. I suspect many might have taken the advice, checked, realised and then kept quiet. Good onya.

I always use a graduated measuring flask for getting the right amount of fluid in the right place - be it gear oil, fork oil or final drive oil...but then check using the tool or other device. The final drive is even more finicky to set the right level and any over fill will head straight in the direction of the rear brake disc.

jumpinjimmy wrote:yes.  I had already drain the transmission and then poured in 850cc and it measured just right.  Thanks for rattling my brain.

88 and myself will be staying down at St Leon sur Vezere in September.

Since this is only a short run south west from you coffee at La Marjolaine in Plazac or lunch over at Roque de St Christophe should be on the cards one of the days we are there. Or bring a tent along for one off the nightly bbqs at the camp site.....We have a bbq up at BobTs house.

sounds fun!