Weeping final drive Nevada 750

Bike is a 2002 750 Nevada classic first reg’d 2005. It has spent most of its life sitting around doing nothing and has 800 miles on the clock, 470 done by me over the last couple of months and believed genuine. I won’t list all the things that have gone wrong so far and which I have either sorted or have on the sorting list, but the one thing I’m having real difficulty with is a persistently weeping rear drive. Weep is from the big cover to hub join, inner seals believed good. So far I have had my friendly local Yamaha dealer fix this twice (second time under their warranty) with new paper gaskets each time. A Yamaha sealant (probably silicone) was applied. Slight improvement, I can now go about 12 miles before weep becomes evident. I checked out earlier threads which advised burping, but mine has the breather fitted, nevertheless I tried loosening this once drive warmed up, but no ‘pop’ of air so I assume breather works. Then I replaced the oil with Agip 85-140, a little better, but still getting a weep. Any ideas? I could try re-sealing joint for the third time, but have no reason to suppose I will make a better job of it than was done at the Yamaha dealer.

If the bike has been left to stand the inner seal may have gone brittle and not be adapting to the expansion of the bevel box when it gets warmer in use. Many seals don’t like being left. I would run it for another 500 and if matters don’t improve, change out the inner seal.

Thanks Kevin, I’ll give that a shot, meanwhile I’ve discovered from another thread that there is a garage in Dunfermline which is close,run by a couple of guys who know about Guzzis. It’s just a shame not to be getting full use out of it cos its a lovely bike to ride.

Now don’t laugh … or take offence, at the suggestion.

Are you sure it is weeping ?

I only ask, as thicko here thought his was, on my V50, after I’d rebuilt it, and it was nothing of the sort, but his right hand rear shocker was leaking, a very very small amount, and it was making the rear hub look like it was weeping from the spindle.

You should have said you were in Scotland. Dunfermline motorcycles are very competent on most makes but they are not Guzzi specialists.
Have you checked that the breather is clear as they often block up. If the drive has been dismantled as far as to check the inner seal it would have been prudent to have changed it. It should be quite obvious if the seal is leaking as the oil will run from behind the hub (16 in picture).The use of silicone sealant on the casing should not be necessary with the gaskets in place either side of the spacer.

You can find videos on rear drive dis-assembly, inspection and re- assembly here:


and a workshop manual (albeit for a breva the rear drive is the same) with pictorial and instruction here:


I would do this work myself on my own bikes sourcing relevant seals from bearing suppliers. HaydnR2013-06-08 23:33:59

Provided the bevel box is not dumping its entire contents onto the floor, I would just clean it up and keep riding

Here are the usual problems re a final drive leak;

  1. Breather. Unscrew and blow through it, making sure it’s not blocked. if
    it’s not vented then oil is forced out at the seals.

  2. Oil level. Some authorities say to fill with the full 170ml, even if that
    amount is over bottom edge of the horizontal oil level check hole. The overfill may put the oil level above the seals, putting them in a constant bath. That’s ok if the seals are good, but will cause a leak if there are any minor problems with the seals.

  3. Seals. Some part(s) in the final drive don’t have good rust protection, and any corroded parts will abrade and damage the seals. If you’re a good mechanic you can replace the two seals and/or their land.

  4. Older style drive hub. The older style drive hub was prone to corrosion and leaks. This was corrected with a newer part, which has chrome plating on the sealing surface.

  5. Bearings. An oil leak can be a sign that the bearings are starting to go
    bad. Replacing the bearings can solve the leak. The bad bearings heat the oil, forcing it out.

6.Casting Flaw. At least one bike had a flaw in the casting, causing the leak. This should only come up on new bikes, and is uncommon, but something to think about.


Thanks folks, all very helpful. The weep does seem to come from the big seal between the cover and the hub. I did put in exactly 170mm when I put the heavier oil in, must get a smaller funnel though. Interesting to hear that breathers can be a problem. I did try blowing through mine and squirted some carb cleaner in, but of course without knowing what a good one should be like it was hard to tell if this one was OK or not. For the sake of a tenner I’ll try a new one. I did wonder about whether sealant should be necessary. I’ll order a new breather and gaskets and take it from there. Meantime I can get to work, about 35 miles without worrying quantities of oil on the rear tyre, but I wouldn’t like to try much further. Already slid off one bike this year…on ice, don’t want to be doing the same trick on my own oil