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Thread: Final drive vent

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  1. #1
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    Final drive vent

    Just went on a spirited three day ride on my 1982 R100 RT, running around 4000 rpm most of the time and a lot of 70 mph stints. The final drive vent throws so much oil it is ridiculous. Every time we stopped i had to wipe things down. I had oil all over the rear tire. The fluid levels were correct to start the ride. There just is no splash guard for the vent. When i look into the boss for the vent, i see the gears. This is a horrible design. Has anyone else had this issue? How did you resolve the issue? I just tried a fix. I'll let you know if mine worked when i take it out next time.

    Thanks,
    Jim O'Coin
    1982 R100RT
    1971 R75/5

  2. #2
    Registered User wvpc's Avatar
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    As the owner of an 83 RT for 3 decades I have never had a catastrophic FD leak. Has the FD been serviced lately? You don't say how many miles are on the bike. Maybe the inexpensive vent plug is faulty? Get a new vent plug and re-service the FD with fresh lube and crush washers.

    Good Luck.
    Last edited by wvpc; 08-21-2013 at 03:33 PM.
    12 R1200 RT
    83 R100 RT

  3. #3
    Registered User toooldtocare's Avatar
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    You said the fluids were the correct level, so this may not be the problem, but on my R90S the same thing happened. Turned out to be the seal on the input shaft to the rear end. Mine went bad and allowed the oil from the drive shaft flow into the rear end, over filling it. A very simple repair.

    Wayne

  4. #4
    Administrator 20774's Avatar
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    What gear oil are you running?
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
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    Just hit 56k miles. I serviced the final drive for driveshaft oil migration two years ago and i know this is not an issue. Should there be a splash plate inside the final drive? That would be the only way to prevent me from seeing the gears. There is no splash plate inside the vent plug. I have been using 80w90 gear oil.

    Thanks
    Jim

  6. #6
    Registered User lmo1131's Avatar
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    You serviced the final drive for driveshaft oil migration two years ago ... conditions do change. Obviously this isn't a "normal" condition; something has failed and is allowing oil to migrate into the FD. There is no splash plate. As mentioned, the shaft seal (#5) has more than likely given up the ghost.



    There are two "weep" holes that may be obstructed. They aren't intended to drain excessive amounts of oil, so you will still need to investigate the cause.

    One below the axle nut,



    the other is adjacent to the drain plug (leading to the spline area).



    Source: http://w6rec.com/duane/bmw/finaldrive/

    Alternatively; you may want to consider rigging a puke line.



    Source: http://www.advrider.com/forums/showthread.php?t=237546
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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