Author Topic: Rear drive leak  (Read 365 times)

Online Scout63

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Rear drive leak
« on: July 02, 2022, 07:40:28 AM »
I rebuilt my G5 rear drive last year with all new oil seals and gaskets, keeping the same shim.  Recently, it leaked the fluid out the bottom.  I took it apart, and everything looks fine.  It looks as if the leak is from the bottom of the inner large oil ring.  I didnít use any gasket sealer on the outer paper shim gasket.  Should I have?  Any thoughts will be appreciated. Thanks,  Ben
Ben Zehnder - Orleans, MA USA
1946 Vincent Rapide
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 Ducati 860GT
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Offline n3303j

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Re: Rear drive leak
« Reply #1 on: July 02, 2022, 09:51:42 AM »
You did replace the hidden seal?



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Online blackcat

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Re: Rear drive leak
« Reply #2 on: July 02, 2022, 10:41:11 AM »
I may have used a gasket sealer like Yamabond on that gasket when I went down the same road, my problem turned out to be the hub which I had to replace. Did you clean up the shoulder with a green scotch bright when you installed the small and large seals?



I don't know the history of the final drive from my LeMans but I assume that when the bike was taken apart it sat backside down on the ground or garage for a long time because the bike didn't have many miles on it when it came into my hands. Funny thing was that when I originally put it back together it didn't leak until it got hot outside, then about two seals later I realized the problem.
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Offline guzzisteve

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Re: Rear drive leak
« Reply #3 on: July 02, 2022, 11:49:12 AM »
I use professional black silicone on outer edge of back plate. If you use anything like a gasket sealer you will not be able to remove cover. Paper gaskets get wet w/water.
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Re: Rear drive leak
« Reply #3 on: July 02, 2022, 11:49:12 AM »

Online Scout63

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Re: Rear drive leak
« Reply #4 on: July 02, 2022, 12:02:01 PM »
I did replace the inner seal and the bearings. The rear drive shoulder is pitted but not nearly as bad as Blackcats. The bike sat for 35 years so the pinion plate is corroded on one half. I dressed the shoulder the best I could. The new Viton large seal still looks fine. I'll reassemble and start looking for a good rear drive. Thanks everyone.
Ben Zehnder - Orleans, MA USA
1946 Vincent Rapide
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 Ducati 860GT
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Online lucian

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Re: Rear drive leak
« Reply #5 on: July 02, 2022, 01:54:11 PM »
Couldn't that hub be turned down and sleeved?

Online blackcat

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Re: Rear drive leak
« Reply #6 on: July 02, 2022, 02:07:02 PM »
Couldn't that hub be turned down and sleeved?

I considered that route but in the end I just bought a new one.
https://www.mgcycle.com/index.php?main_page=product_info&cPath=72&products_id=707
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Online spmoto

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Re: Rear drive leak
« Reply #7 on: July 02, 2022, 04:21:06 PM »
I had the same problem and two seals later it still leaked. My hub had a small nick at the outer edge. I polished the heck out of it and it still leaked. I had also been "burping" the box each time...no luck. I ended up replacing the rear hub and problem solved. Still a good idea to burp it though I think.

Online Scout63

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Re: Rear drive leak
« Reply #8 on: July 02, 2022, 09:38:01 PM »
I worked on it some more with a green scotch brite but it really wonít smooth out. I put it back together and cleaned up the back end nicely.  It isnít leaking after about twenty miles, but Iím sure it will. I ordered the new drive from MG Cycle and a couple of new viton seals.  Next time it leaks Iíll swap it out. You guys are the best.


seals. 
Ben Zehnder - Orleans, MA USA
1946 Vincent Rapide
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 Ducati 860GT
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Offline guzziart

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Re: Rear drive leak
« Reply #9 on: July 05, 2022, 07:58:48 AM »
FWIW, my rear drive leak turned out to be the shim.  Apparently the shim had corroded to a point where a slight path had developed to allow gear oil to leak past the paper seals and drip onto the wheel.  I realized the shim was my problem the 2nd time I took the drive apart.  Anyway, if your shim has the slightest amount of rust on it you may want to consider replacing it too, they were about $10 in 2010.  I know you can clean them but the pitting will still be there.

Art
'72 Eldo, '72 CL350, '81 CB125s, '87 LMIVSE, '91 CT70, '03 V11 Lemans, '08 Wing & '12 Wee Strom

Online Scout63

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Re: Rear drive leak
« Reply #10 on: July 05, 2022, 06:06:41 PM »
FWIW, my rear drive leak turned out to be the shim.  Apparently the shim had corroded to a point where a slight path had developed to allow gear oil to leak past the paper seals and drip onto the wheel.  I realized the shim was my problem the 2nd time I took the drive apart.  Anyway, if your shim has the slightest amount of rust on it you may want to consider replacing it too, they were about $10 in 2010.  I know you can clean them but the pitting will still be there.

Art

Interesting. Iíll have it apart again soon so will check the shim also.
Ben Zehnder - Orleans, MA USA
1946 Vincent Rapide
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 Ducati 860GT
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Online Antietam Classic Cycle

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Re: Rear drive leak
« Reply #11 on: July 05, 2022, 06:25:10 PM »
A light coating of sealer doesn't hurt, especially if the shim is less than perfectly smooth. I use Permatex 300 or Aviation (small bottle, brown liquid).
Charlie

 

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