Author Topic: Breva 750 oil leak from rear drive  (Read 3364 times)

Offline rathlindri

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Breva 750 oil leak from rear drive
« on: June 04, 2015, 04:11:03 AM »
I have noticed spots of transmission oil on the rear wheel rim on my 750 Breva recently, it appears to be coming from the bottom of the rear drive bevel unit and I'm assuming a seal in there is starting to fail. All drain and level plugs are dry. Doesn't leak when 'bike isn't being used, only during a ride. Is this a known fault and how easy is it to fix?

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Re: Breva 750 oil leak from rear drive
« Reply #1 on: June 04, 2015, 06:45:58 AM »
It's a known fault that seals sometimes fail. Older the seal? Greater the chance of failure. All B75's are no longer new.

Having said that smallblocks are more prone to seal failure than big blocks and I'm afraid replacing the seal is a bit of a prick of a job.

Someone quite recently did a very nice photoessay on the process. Perhaps someone can point you to it? Somebody will of bookmarked it.

Pete


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Re: Breva 750 oil leak from rear drive
« Reply #2 on: June 04, 2015, 01:07:01 PM »
Here's my 2 cents on possible faults;

1. Breather.  On top of the final final drive is a vented bolt.   if it's not vented then oil is forced out at the seals when it's running.  My vent become blocked one year, for no apparent reason.

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.  One part that might rust is part no. 16 "pin" or hub in the factory parts diagram, and the seals often affected are no. 15 and 3.  If you try to order a new hub or pin, see note 4 below.  Once you are in this deep it is best to replace both seals.  Reportedly, getting to them will require an impact driver to get the 6 bolts off of the inside of the drive.  Also, getting the seal off will be difficult due to the inner race for the needle roller on the flange.  To remove, clean oil off and dry it to get a good grip.  Hold it, and strike the hub with a rawhide mallet.  This will usually get it off.  Failing that, a shop can press it out.
   Often the leak is usually the seal, not the gasket, however some have reported that replacing the shim between the gasket and seal solves the leak. You could try this and see if it works.
   If the seal land is corroded, then the only fix is to repair the damaged seal land with a stainless seal land repair ring.  Parts are cheap, but it takes a day for dismantling and reassembly.  A bear track puller is needed to remove part no. 5, the roller bearing. 

4. Older style drive hub.  The older style drive hub was prone to leaks.  This was corrected with a newer part, which has chrome plating on the sealing surface.  Your bike might have been built with the old part.  However, it appears that there is a dimensional change between the old and new style pin (or hub) and they are not interchangeable.  Also note that they are often mis-labeled in warehouses, so when you order an old/new one you might not get the right one.

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

Keep me posted on your progress,
Joe
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Offline rathlindri

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Re: Breva 750 oil leak from rear drive
« Reply #3 on: June 05, 2015, 03:15:05 AM »
Thanks for the replies guys. I recently changed the rear transmission oil and after completely draining added the correct 170 ml. Guess what, I checked the level yesterday and probably about 15-20 mls flowed out. Hoping that was the issue. Breather plug working okay. If it still leaks now it has to be the seals or bearings?
Will advise shortly. What a great forum this is!

Offline Brevaman

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Re: Breva 750 oil leak from rear drive
« Reply #4 on: October 29, 2016, 05:00:46 PM »
I had what I thought was a leaky final drive seal on my new-to-me '07 Breva 750. 
Thanks to Sign216, I checked the venting fill plug.  It was frozen but some gentle tapping and twisting with pliers got it moving.  Guess what??  Leaking gone!!

I've learned over the years that it's often the simple things that solve the problem.  Thanks to the internet and these forums, we can really use our collective wisdom for the benefit of each other.  That little tip saved me from an involved and unnecessary job.  I AM GRATEFUL!!
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Re: Breva 750 oil leak from rear drive
« Reply #5 on: October 29, 2016, 09:43:46 PM »
Every time I change the oil in the rear end I make sure the vent is clear. Look on it as part of the maintenance.
Muzz. Cristchurch, New Zealand
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Re: Breva 750 oil leak from rear drive
« Reply #6 on: October 30, 2016, 11:38:33 AM »
I had what I thought was a leaky final drive seal on my new-to-me '07 Breva 750. 
Thanks to Sign216, I checked the venting fill plug.  It was frozen but some gentle tapping and twisting with pliers got it moving.  Guess what??  Leaking gone!!

I've learned over the years that it's often the simple things that solve the problem.  Thanks to the internet and these forums, we can really use our collective wisdom for the benefit of each other.  That little tip saved me from an involved and unnecessary job.  I AM GRATEFUL!!

Brevaman,
Glad my idea worked, and glad it was the simplest thing in the list.
Hope to see you at a New England Guzzi event.
Joe
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Offline malik

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Re: Breva 750 oil leak from rear drive
« Reply #7 on: October 30, 2016, 07:46:27 PM »
Also note that using synthetic 140 oil in the final drive appears to induce occasional leaking on long trips. The solution for both the v7s was to revert to the mineral 85w140. I used a mix of 120ml of 85w140 and 50ml of Nulon G70 for a couple of fills, and now only 170ml of the 85w140. No leaking now.
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Online Chuck in Indiana

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Re: Breva 750 oil leak from rear drive
« Reply #8 on: October 31, 2016, 07:00:20 AM »
Caution.. oil thread..  :smiley:
I only use dino oil with moly in the rear drive of small blocks. That PITA inner seal tends to leak with synthetic.
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Re: Breva 750 oil leak from rear drive
« Reply #9 on: October 31, 2016, 02:37:12 PM »
Caution.. oil thread..  :smiley:
I only use dino oil with moly in the rear drive of small blocks. That PITA inner seal tends to leak with synthetic.

 :1: Me also Chuck. Leaking seals and synthetics problems were surfacing fairly early on.

Funnily, I had no end of problems sourcing the moly last time. My bottle fell off the shelf in the earthquake we had a few years ago, and by the time I realised in I had a non-slip garage floor and enough left for one fill. :cry: Finally found the last one that was left in Christchurch I think.
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Offline Brevaman

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Re: Breva 750 oil leak from rear drive
« Reply #10 on: April 25, 2017, 03:32:00 PM »
I guess I'll have to try a dino based oil then.....
Unfortunately, the vent wasn't clogged as I'm now seeing oil on the right side of the wheel after every ride. :cry:
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Re: Breva 750 oil leak from rear drive
« Reply #11 on: April 26, 2017, 04:35:37 PM »
I guess I'll have to try a dino based oil then.....
Unfortunately, the vent wasn't clogged as I'm now seeing oil on the right side of the wheel after every ride. :cry:

Brevaman,

Look at my post of a year ago and let me know how it works out.  Dino oil, alone, is unlikely to be the complete answer but I hope for the best.

Joe
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Re: Breva 750 oil leak from rear drive
« Reply #12 on: April 26, 2017, 04:48:21 PM »
 :1: on that.

It was actually Sign that alerted us to the possibility of the blocked vent. Now cleaned each time I do the diff. I am now reassured when I see the faint oil mist deposit around the vent.
Muzz. Cristchurch, New Zealand
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Re: Breva 750 oil leak from rear drive
« Reply #13 on: April 26, 2017, 05:00:51 PM »
:1: on that.

It was actually Sign that alerted us to the possibility of the blocked vent. Now cleaned each time I do the diff. I am now reassured when I see the faint oil mist deposit around the vent.

Muzz,

You are a Master of the 750.  A kind word from you, and I feel vindicated.

Joe
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Re: Breva 750 oil leak from rear drive
« Reply #14 on: April 27, 2017, 02:26:58 AM »
Muzz,

You are a Master of the 750.  A kind word from you, and I feel vindicated.

Joe

Blushes. :embarrassed:

Hardly! Just because I have personally named every part of the gearbox! :evil: I am still learning. I have only set plug gaps and valve clearances, done fluid changes and blown out air filter on the motor. It purrs like a kitty cat. If it ain't broke. don't fix it. Change diff oil. Gearbox has been fine since Steamdriven and myself replaced the jamming non-jam :rolleyes: gear selector fork with a second hand one as delivered by the inimitable Pete Roper. :thumb: Runs like a Swiss watch. Now all I do is hit the button and  :bike-037:. (fingers crossed :grin:)
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Offline Yard Sale

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Re: Breva 750 oil leak from rear drive
« Reply #15 on: May 10, 2018, 11:02:37 PM »
Someone quite recently did a very nice photoessay on the process. Perhaps someone can point you to it? Somebody will of bookmarked it.
Bump

I would appreciate a link to those photos. My B750 is leaking from the final drive.

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Re: Breva 750 oil leak from rear drive
« Reply #16 on: May 10, 2018, 11:09:59 PM »
Bump

I would appreciate a link to those photos. My B750 is leaking from the final drive.

There is one for the gearbox, written very humerously by Nick Webb because the official Guzzi one is pretty wide of the Mark. Didn't know there was one for the final drive.

http://www.thisoldtractor.com/guzzitech.dk/pdf/gearbox-repair-breva-750-nick-webb.pdf
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Online SmithSwede

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Re: Breva 750 oil leak from rear drive
« Reply #17 on: May 10, 2018, 11:35:49 PM »
Muzz, if you know Nick, please pass along my immense and sincere appreciation for the efforts he took to create that tutorial.  I recently replaced the clutch and an input shaft bearing on my V7, and the two things that kept me going on this project was my own Southern pig-headed stubbornness and that excellent, detailed, and humorous tutorial.   I read it about a dozen times.

Back to the main topic.  Whenever I change the transmission or final drive oil, I make a point of removing the vent, shooting it full of WD-40, and blowing it out with lots of compressed air.   Maybe that is overkill, but I sleep better knowing that my vents will, indeed, vent. 
« Last Edit: May 10, 2018, 11:37:38 PM by SmithSwede »
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Re: Breva 750 oil leak from rear drive
« Reply #18 on: May 11, 2018, 04:31:44 AM »
SS, some time back I sent Nick a pm but he never replied and I have not seen him post for years.

It certainly was an interesting time as we blundered through the innards of our respective bikes. :rolleyes: I too refer to his most excellent article; I have had mine out three times now. :evil:
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Offline romanoaf

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Re: Breva 750 oil leak from rear drive
« Reply #19 on: May 11, 2018, 07:59:54 AM »
I've recently re-sealed mine- my leaks were the paper gaskets from the housing to the hub. Not a difficult job, but can require a puller (or careful mallet use)
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Offline cheshirelad

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Re: Breva 750 oil leak from rear drive
« Reply #20 on: July 07, 2019, 04:27:14 AM »
Good morning to all from a sunny Cheshire,
         I have only owned my 03 750 Breva for 2 months but have noticed a 'spiders web' of fluid on the rear hub after a Sunday run. No sign of a leak from drain plug or any of the other plugs, so at a bit of a loss. I've read on the site about cleaning the vent. So I'll try and remove what appears to be a dust cap when I figure out if it pings off or screws off, (don't want to damage it). Then I assume the filler plug on top of the hub just screws off normally then it can be cleaned and blown through with my airline. The bike has only done 6000 miles in 16 years so I hope all the seals will not need replacing. I'm no mechanic but will have a go at the simple jobs if one of our knowledgeable members can point me in the right direction. Many thanks in anticipation. Ted R.

Online Chuck in Indiana

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Re: Breva 750 oil leak from rear drive
« Reply #21 on: July 07, 2019, 05:36:38 AM »
Quote
I've read on the site about cleaning the vent. So I'll try and remove what appears to be a dust cap when I figure out if it pings off or screws off, (don't want to damage it).
It just screws off.. the "dust cap" is part of the assembly.
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Re: Breva 750 oil leak from rear drive
« Reply #22 on: July 07, 2019, 07:13:18 AM »
I was dismayed to find my V50II leaking rear drive oil shortly after I had changed the seals.    The bevel box had inadvertently been filled with synthetic oil, I discovered.  Drained the synthetic, replaced it with Dino oil - no further leaks.  Why this is the case is a mystery, but the observations above from Malik and Chuck are right on target.  Synthetic indeed causes indigestion and leaks in small block rear drives. 
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Online Chuck in Indiana

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Re: Breva 750 oil leak from rear drive
« Reply #23 on: July 07, 2019, 08:15:57 AM »
Quote
replaced it with Dino oil - no further leaks.  Why this is the case is a mystery,

Not mysterious, really. The shaft the inner seal rides on isn't protected from the elements very well and tends to corrode. Synthetic oil is very good at finding a way to get past a less than pristine seal surface.  :smiley:
Chuck in (Elwood) Indiana/sometimes SoCal

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Offline malik

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Re: Breva 750 oil leak from rear drive
« Reply #24 on: July 07, 2019, 02:06:48 PM »
You are saying that our seal surfaces are less than pristine! Fie, Fie. Oh, the Shame!

Makes sense - came across an early big block that had a persistent final drive leak. Re-sealed & rebuilt multiple times. Problem didn't go away until he replaced the casing.
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Re: Breva 750 oil leak from rear drive
« Reply #25 on: July 07, 2019, 07:54:58 PM »
You are saying that our seal surfaces are less than pristine! Fie, Fie. Oh, the Shame!

Makes sense - came across an early big block that had a persistent final drive leak. Re-sealed & rebuilt multiple times. Problem didn't go away until he replaced the casing.
`

I have heard that before:  that the case surfaces can be the source of a persistent leak, not the seals.
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Offline Yard Sale

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Re: Breva 750 oil leak from rear drive
« Reply #26 on: July 14, 2019, 10:28:36 AM »
I've got the final drive off and partially apart. I assume the large seal is the source of oil leaking on the rear wheel and tire. At what point am I going to need special tools? I have small blind bearing pullers but that's it.








Online Chuck in Indiana

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Re: Breva 750 oil leak from rear drive
« Reply #27 on: July 14, 2019, 11:24:59 AM »
Quote
I assume the large seal is the source of oil leaking on the rear wheel and tire.
What makes you assume that? Do you have a picture of the leak before disassembly?
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Re: Breva 750 oil leak from rear drive
« Reply #28 on: July 15, 2019, 09:59:25 AM »
Upon further inspection, the leak is not coming from the axial center of the cover, so it's not the large seal. It's leaking radially between the cover and the housing. Good news, it might just be the paper gaskets, right? Bad news, it could require re-shimming, or worse, the mating surfaces are borked.

I think I might just try new gaskets at this point.

Screen grab from MG shop video. Large seal leak would put oil on the cover here, wouldn't it?




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