Nevada rear drive leak - fixed itself ?

[s151669]

My Nevada seems to have mind of it's own. Just as I pressed order on bunch of parts, the rear drive started to leak. There was a coin sized oil stain on the rear wheel. Definitely smells like oil.

Oh well, I can get the seals from local bearing supplier. And I was going to take the rear drive off anyway.

However, I have kept riding the thing and it seems that it does not leak oil anymore. Not a drop to be seen, rear drive casing is bone dry.

What just happened ?

[Dukedesmo]

As a Land Rover owner, as long as it is leaking you know there is oil in it - have you checked the level?


On a more serious note, can overfilling cause a leak?

[Frenchfrog]

my small block did exacatly the same but erratically.In my case I think it was because the casing was over pressurizing when I was driving hard and in high summer heats.I solved it by modifying the venting system in order to have a venting tube leading up over the top of the frame which allows the oil to expand and vent but go back into the casing when the pressure lowers.

[s151669]

Level was checked last year when the full contents leaked from the drain hole due missing aluminium washer. Filled until overflowed from the rear hole. Checked the breather while I was at it and it flowed freely both ways.

[Dukedesmo]

The over pressurising as above sounds a likely cause, does it have a vent?

[Tkelly]

Sounds like it is ok since you recently filled it and it isn’t leaking now.

[s151669]

Well, checked the breather again. Basically it is a tube with "umbrella" over it. Before the "umbrella" was rotating freely and it had some vertical motion too. Now it was stuck in place very hard. Seems that combination of oil fumes and dust had done their work and rendered the breather non breathing.

Of course I could have verified that if I had removed the breather and tried to blow through it but now that I jiggled the "umbrella" free I can't do it anymore until that happens again ;-)

Hopefully that was it.

[sign216]

Well, checked the breather again. Basically it is a tube with "umbrella" over it. Before the "umbrella" was rotating freely and it had some vertical motion too. Now it was stuck in place very hard. Seems that combination of oil fumes and dust had done their work and rendered the breather non breathing.

Of course I could have verified that if I had removed the breather and tried to blow through it but now that I jiggled the "umbrella" free I can't do it anymore until that happens again ;-)

Hopefully that was it.

Yep, the breather on my V7 closed up too.  I cut a line in the top to open it up.  Water might get in when I ride in the rain, but the bike is stored sheltered.

[Frenchfrog]

You can use the spigot on the breather to fit a breather tube that then can run high up on the frame to eliminate any breathing issues.Looks a bit McGyver but works and stops those leaks onto the tyre as long as the seals are good.

[s151669]

Oh well, that would have been too easy. Leaks again, now more.

So, rear drive off. Wheel shaft hole bone dry - sans whatever is left from grease of shaft. Rim of the rear drive bone dry. But when separated from swing arm - oh well. Oil inside swing arm. Mostly at drive end (doh, it is the lowest point) and some in the boot (doh, it is local lowest point).  Seems to be blackish (aka contains moly). Transmission end seems to be dry, only things found there are remnants of spline grease.

So, it seems to be the seal in the rear drive facing the drive shaft. And the oil leaks from the joint between rear drive and swing arm. Maybe ?

Can the seal be swapped by hooking it away or does it require disassembling the pinion assembly ?

Flexible joint at driveshaft seems to have no play so good to go ?

Left side swing arm bearing needs to be replaced. Rusted.

Any tips on reassembling the swing arm / drive shaft / rear drive combination ?

[s151669]

Ok.

Plot thickens. I finally had some time to do some wrenching.

The drive shaft side seal of bevel box - how deep it is supposed to go ? To the bottom ? The depth of the hole is like twice the thickness of the seal. Cause of leak could be that outermost part of the shaft is rusted - and the seal was riding on that. What is going on here ?

[Pescatore]

Can you upload a picture?

[s151669]

Does this work ?

https://ibb.co/yFV9gJTb

The hole is indeed twice as deep as the seal is but the seal was at the top. No wonder it did not seal when you look at the shaft.

[sign216]

Does this work ?

https://ibb.co/yFV9gJTb

The hole is indeed twice as deep as the seal is but the seal was at the top. No wonder it did not seal when you look at the shaft.

s151669,
Try this Guzzi smallblock group.  They specialize older smallblocks, and should have helpful experience.

https://groups.io/g/Moto-Guzzi-SmallBlock

Joe

[Kiwi_Roy]

So it stopped leaking once all the oil had run out, that's not good.

[Pescatore]

Have you tried pushing the seal back down?

[s151669]

So it stopped leaking once all the oil had run out, that's not good.

 

Nope. Plenty of oil left.

Have you tried pushing the seal back down?

The seal was toast anyway. New one is installed and bevel drive is back on bike. Now it just needs correct amount of new oil...

[s151669]

And plot thickens: new seal leaks too.

And the mechanism indeed is that oil runs through the cardan tunnel into the boot and leaks from there and runs under swing arm until it drops at the drain bolt into the tire.

Now what ? There is a junk yard where there is a "new" rear drive. But guess what: it leaks from the same seal too. So this seems to be a common issue so I guess there should be a common solution. Better drive shaft boot and overfill the rear drive ? Get a Japaninc bike instead ? 

Oh well, nothing that can be done today --> 

[faffi]

If the oil comes from the shaft tunnel, wouldn't that suggest a leaking output seal from the transmission Or am I missing something? In most bikes, the shaft/cardan tunnel is dry.

[s151669]

If the oil comes from the shaft tunnel, wouldn't that suggest a leaking output seal from the transmission Or am I missing something? In most bikes, the shaft/cardan tunnel is dry.

It would, except that the "tube" at transmission side is dry. And oil is black due moly additive, transmission side is yellowish.

It seems that oil leaks from final drive to almost horizontal cardan tunnel and - either due braking or driving down hill eventually reaches the boot and leaks from there.

As the leak must be between the spacer and seal I think I just try flipping the spacer (and remove the rust) to get unused surface for the seal.

[s151669]

Oh well. Spacer is not symmetrical after all.

I got the nut off with deep socket and impact wrench. Polished the spacer, now I just need to put the thing back together.