Main shaft leak

[roadie]

Hello all, I was hoping to get some help with a persistent leak.
The shop I go to and where I bought my 1979 900ss from, has tried to fix this leak twice now. First they replaced the mains haft seal, still leaked. Then they replaced the two seals behind there ( as they told me, I haven't been in there myself yet). It didn't leak after there test ride but after I picked it up yesterday and took it for a spin it was still leaking.
Any tips to try and fix this myself? I've heard that the main shaft nut needs to be really cranked on but needs a special tool to do so?
Also my 900ss has no trip meter to reset, how do you guys know when to fill up?
Thanks, sorry for the newbie-ish questions.
Rod

[machten]

The shop I go to and where I bought my 1979 900ss from, has tried to fix this leak twice now. First they replaced the mains haft seal, still leaked. Then they replaced the two seals behind there ( as they told me, I haven't been in there myself yet). It didn't leak after there test ride but after I picked it up yesterday and took it for a spin it was still leaking.

Do you mean the drive shaft/counter shaft gear that the front sprocket sits on? The main shaft is different and is internal to the gear box and provides drive to the drive/counter shaft. Are you talking about an oil leak around the front sprocket?

Kev

[roadie]

Hi, thanks for the reply.
Yes, the leak is around the front spocket. This bike is fairly new to me, still learning.
Much appreciated,
Rod

[BevHevSteve]

You can fit up to 3 or 4 of the small seals in there. The locknut MUST be very tight that holds the countershaft sprocket on... I use a drop of blue loctite. The large outer seal is a possible source of the leak as well.

You can check to see EXACTLY where the leak is, but cleaning everything up very well, then spray so aerosol foot spray [the white powder stuff] around the area then fire the bike up. The leak will show itself quickly by wetting the white powder, then you will know where to put your efforts.

Lastly, you might just be over lubing your chain.......

[roadie]

Thanks! I'm thinking the countershaft sprocket needs a good tighten. Any idea of the torque spec or a schematic to check out?

[roadie]

Thanks Steve, I did a search and found reference to a special socket for tightening the nut, do you have these in stock? Didn't see any on your shop page.

[BevHevSteve]

sold out the run I did last year of them, and just put in an order for more with my machinist. I thionk it might be a month before I have them though. If you want me to notify you, email me.

[wdietz186]

This has been covered some time ago but it helps to put some sealer on each side of the sprocket [between the sprocket and spacer and under the nut/lock tab] as the splines for the sprocket are cut deeply on the output gear and end behind the bearing in the case. This allows oil to creep into the splines and gets thrown out on each side of the sprocket. The nut does need to be plenty tight but unless the surfaces are absolutely true[they never are] some oil will get thrown out.

[ducadini]

Before You indulge Yourself in heavy wrenching, if the breather tube exiting the crankcase behind the rear cilinder is obstructed, it usually starts leaking in the sprocket area, shifting axle or main shaft seals.
Minimum diameter of the tube must be the same as the bore of the black cap.
If a clear tube is fitted, be sure it can take some heating without flattening , that's why originally a spring was inserted in the first part of the black tube.
cu
ducadini

[Craig in France]

Just to add a little to what others have said (and please correct me, guys, when I've erred anywhere or missed something out).
P.s The answer to 'What torque ...?' is in point 5 below . But read on ...

There are 2 possible sources of a leak in this area:

1. The seals on the gearbox drive shaft.
2. The seal behind the neutral indicator switch.



The most frequent culprit is the larger of the seals behind the drive sprocket - marked 1a in the picture above. So I’ll deal with that for now.

To remedy it, you need to remove the old one and replace it. Its size is 45x60x10 and it's part no. is 0647.49.325.
Note: This seal and the tools mentioned below should all be available from your preferred Ducati specialist supplier.

Take the cover off, and prise back the tab(s) of the lock washer. Now you need to use the correct tools to remove the sprocket: first, the one to turn the sprocket nut ...



The second to hold the sprocket still.



You can devise a method of locking up the sprocket that does not require the use of this second special tool. But I don’t advise this approach -see point 5 below for one reason why; so I’m not going to tell you how !

Note: When you buy one of these tools, try to get one that can be used with both 15 and 16 tooth sprockets. Now, it's possible that that is all that is available these days, anyway; but, believe it or not, the original Ducati tool was either for 15 tooth .. or for 16. So you could finding yourself needing both ... .

Once the sprocket is off, it’s the turn of the seal. To remove this, you need to carefully drill two small holes right thru the seal. Into these holes you screw two appropriately sized self-tapping screws. Leave enuf of these screws projecting so that you can grab hold of them with some mole-grip pliers, one set of pliers on each screw. And pull. The seal will come out. It may take some pulling and pleading, but it will come …

You then install the new seal. (Personally, I lube the seal with a light trace of grease to ease insertion). Make sure it is fitted flush. Further re-assembly is the reverse of the disassembly. Again, you need to use the two special tools. Some other points:

1. The sprocket goes back with the wider boss facing OUT.

2. The lock nut goes back with the chamfered face up against the tab washer. And you should consider changing the tab washer for a new one.

3. As stated above, you can consider using a little silicone or Loctite on the lock nut. The silicone trick was one that was told to me by a certain Steve Wynn (who also recommended using two of the lock nuts - your choice).

4. There is also available a lock nut with a nylon inner seal. I got one some time ago, can't I remember from where now; but I have a note that the SKF reference is GUK7.

5. The torque loading on the nut should be 70-84 ft/lb (100-120 Nm). That, in plain English, is tight … and then some. And THAT alone is a very good reason why you should use the proper tool for locking up the sprocket .

HTH

Craig

[roadie]

Wow, thanks for the very detailed responses! This helps a lot. The shop I go to has offered to fix the leak for free but this would be the third time I've had it in for this. Need the tools and then I'm happy to give it a go myself.
Awesome forum, thanks Steve for putting it up.
Rod

[Craig in France]

Wow, thanks for the very detailed responses

No worries Rod. But please note: I’ve had to edit my original posting - I made an idiot of myself, confusing the situation with what happens on another bike I’ve just done ... .

So, just to be clear: the main potential source of leaks are the TWO seals on the gearbox drive shaft, in the locations marked 1a and 1b here:



1a, the most likely culprit, is the big one whose replacement I covered in my original post. But in addition there is a little seal in position 1b that looks like this … (photo courtesy of Steve, btw):



Its dimensions are 22x28x4, part # 0755.16.105. And, as Steve has indicated, it’s renewal is easy. First, there is an internal circlip that you need to carefully prise out. Then, leaving the original seal in place, simply push in a new seal, over the top of the existing one. I know Steve reckons it does no harm to fit a couple at the same time, btw - there is enuf space. Don’t forget to refit the circlip.

The shop I go to has offered to fix the leak for free, but this would be the third time I've had it in for this. Need the tools and then I'm happy to give it a go myself.

Yeh, there's really no good reason why someone competent should need more than one go at stopping your leak. So I think you're right to try yourself .

Get the two tools, and buy both of the new seals and a tab washer at the same time. But, before you do anything, first try tightening the sprocket nut up to the right torque. You may very well find it simply wasn't tight enuf ...

If this works, you can keep the seals and tab washer in your spares box ... ready for the next time !

Ciao

Craig

[machten]

Fron wdietz...

This has been covered some time ago but it helps to put some sealer on each side of the sprocket [between the sprocket and spacer and under the nut/lock tab] as the splines for the sprocket are cut deeply on the output gear and end behind the bearing in the case. This allows oil to creep into the splines and gets thrown out on each side of the sprocket.

Exactly! I also find what helps if you are rebuilding an engine is to to put an o-ring between the countershaft face and the bearing, It's not in the parts manual, but it works a treat to help seal those splines that are a tad too long.

Kev

[Craig in France]

Hey Kev, am I right in thinking it was you who also had a leak from the pesky indicator switch?

(Did you see the complete bull I wote the first time round? If not, good. If yes ... you didn't say nowt )

Ciao

Craig

[machten]

Hey Kev, am I right in thinking it was you who also had a leak from the pesky indicator switch?

Hiya Craig. At some stage I either did have such a leak, or initially thought I did and it turned out to be the countershaft. I honestly can't remember which!

One of the problems with having a few bevels is remembering what I've done to what bike. I write down the big stuff and the regular maintenance, but the things in between slip through the cracks and there's never any shortage of things to be done.

I can't even see if I have a leak there at the moment as the 78 Darmah is off the road with a clean engine and the heads off waiting for me strip them for new valve guides and seats (for about 6 months now)...
I'll get to that after I get my GT wheels respoked and re shod...
I'll get to that after I do the valve shimming on my 250 desmo and fix a tacho drive oil leak...
I'll get to that after I fix a countershaft leak on the Sport...

And that's only the "must do" things...Sigh!

How much does one of those Sport classic GT's go for these days?

(Did you see the complete bull I wote the first time round? If not, good. If yes ... you didn't say nowt )

Never saw a thing! Like a doctor, by the time I got here, you'd buried your mistake! - And see above - I have the same problem!

Kev