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Thread: Oil leak drive shaft boot

  1. #16
    Quote Originally Posted by lkchris View Post
    The boot exists for dirt/dust shielding. It is NOT for oil retention. You have a leaking seal at rear of transmission.
    I guess the oil in the driveshaft housing that is there from the factory isn't supposed to be there?
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  2. #17
    Registered User toooldtocare's Avatar
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    Quote Originally Posted by SCBuckeye View Post
    I guess the oil in the driveshaft housing that is there from the factory isn't supposed to be there?
    Yeah, and they have been doing it that for decades. You think they would get it right, some day. Oh, I forgot, they stopped putting oil in the driveshaft when they stopped making the airhead.

  3. #18
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    I am "reviving" this old thread as I came across it doing a search on oil dripping off the rubber boot on my 1972 R 75/5.
    I don't have any experience on this and just started looking for some advice as I had the bike on my lift and was running it to sync the carbs so it was running for awhile (with fans in front of cylinders). I had noticed previously that there was a bit of oil around the boot and on the center stand (from blow back from the boot, I presume), but this is the first time that I noticed a fair amount of dripping.... I think, because the oil was hot and I had never seen the undercarriage when the bike had ever been at those temperatures.

    I am wondering if a '72 /5 model has a similar set up as the model discussed in this post, as one of the posts said this was similar on all airheads. I am hoping that it just needs a new boot, or possibly loose clamps(haven't checked that yet).

    Thanks for any advice.

  4. #19
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by 2wheeljunkie View Post
    I am "reviving" this old thread as I came across it doing a search on oil dripping off the rubber boot on my 1972 R 75/5.
    I don't have any experience on this and just started looking for some advice as I had the bike on my lift and was running it to sync the carbs so it was running for awhile (with fans in front of cylinders). I had noticed previously that there was a bit of oil around the boot and on the center stand (from blow back from the boot, I presume), but this is the first time that I noticed a fair amount of dripping.... I think, because the oil was hot and I had never seen the undercarriage when the bike had ever been at those temperatures.

    I am wondering if a '72 /5 model has a similar set up as the model discussed in this post, as one of the posts said this was similar on all airheads. I am hoping that it just needs a new boot, or possibly loose clamps(haven't checked that yet).

    Thanks for any advice.
    Under normal conditions the gear oil at the end of the drive shaft where it connects to the rear drive stays there and the boot at the swing arm pivot only has to keep dirt out and oil mist in. However, there is almost always some oil which collects in the bottom pleats of that boot over time from the oil mist. So, if you drive shaft boot is failing, then there's your leak.

    I would start by cleaning the boot and then going over it with a flashlight and my fingers to see if I could find any damage, wear, or tears. Finding none, then check the hose clamp tightness. If they are very loose, then tighten and test ride. However, those clamps tend to stay put, so if they are ok then I would pull back the end attached to the transmission and look for signs of gear oil coming through the transmission vent hole (drilled into the face of the gear box cover behind the output shaft flange). You might need to rotate the drive shaft flange to see that hole. This may not be a conclusive inspection, in which case I would also check the transmission oil level. It's kind of hard to over fill, but it can get water contamination because of a failed speedometer cable boot and water can make the gear oil foam which might cause some to pass into the drive shaft housing.

    Having said all that, your most likely problem is an bad drive shaft boot. Unless you have changed it or know that someone else did, then it's 50 years old and even the good German rubber of the day doesn't last forever.
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  5. #20
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    Quote Originally Posted by GREGFEELER View Post
    Under normal conditions the gear oil at the end of the drive shaft where it connects to the rear drive stays there and the boot at the swing arm pivot only has to keep dirt out and oil mist in. However, there is almost always some oil which collects in the bottom pleats of that boot over time from the oil mist. So, if you drive shaft boot is failing, then there's your leak.

    I would start by cleaning the boot and then going over it with a flashlight and my fingers to see if I could find any damage, wear, or tears. Finding none, then check the hose clamp tightness. If they are very loose, then tighten and test ride. However, those clamps tend to stay put, so if they are ok then I would pull back the end attached to the transmission and look for signs of gear oil coming through the transmission vent hole (drilled into the face of the gear box cover behind the output shaft flange). You might need to rotate the drive shaft flange to see that hole. This may not be a conclusive inspection, in which case I would also check the transmission oil level. It's kind of hard to over fill, but it can get water contamination because of a failed speedometer cable boot and water can make the gear oil foam which might cause some to pass into the drive shaft housing.

    Having said all that, your most likely problem is an bad drive shaft boot. Unless you have changed it or know that someone else did, then it's 50 years old and even the good German rubber of the day doesn't last forever.

    Thanks for the info. I am not sure of the age of the boot as the bike was redone a few years ago by the previous owner and I'm not sure if that boot was changed or not. I have a box of original parts that were replaced and I don't recall seeing that boot....but it could have been so dirty and worn that it just got tossed. I will look closer at the boot now that I know about the oil mist and oil collection inside the boot. From what I have seen blown back on the center stand and surrounding area it does not look like a major amount of oil, so I don't think I have a big problem.

  6. #21
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by 2wheeljunkie View Post
    Thanks for the info. I am not sure of the age of the boot as the bike was redone a few years ago by the previous owner and I'm not sure if that boot was changed or not. I have a box of original parts that were replaced and I don't recall seeing that boot....but it could have been so dirty and worn that it just got tossed. I will look closer at the boot now that I know about the oil mist and oil collection inside the boot. From what I have seen blown back on the center stand and surrounding area it does not look like a major amount of oil, so I don't think I have a big problem.
    I'd bet the PO put on a new boot. Possible that he didn't get it on with a good seal, but a physical inspection should tell the tail.
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  7. #22
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    There is orientation to the boot. One side has to be on the transmission side and "up".
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
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  8. #23
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    Thanks to all for the info. I haven't had time to check any further on the boot, other than to look at it, and it is definitely 50 years old, so I believe it was replaced when the bike was rebuilt. I did tighten the one clamp, but can't get at the screw on the other one until I get the bike back on the lift and have more visibility. I don't want to start the bike just to drive it up the ramp on the lift and I no longer have the strength to push it on.

  9. #24
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    Be sure and check how the boot is situated on either side. The clamp might be tight, but if it's not in the groove it needs to be in, it will still leak.
    Kurt -- Forum Liaison ---> 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!

  10. #25
    Registered User STEVENRANKIN's Avatar
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    Pain

    These boots have been one of the biggest pain designs BMW did on both the twin shock bikes and the mono shock bikes.

    They do age and crack and leak. It is very rare to have a transmission seal leak, more common the boot cracks as it is exposed to all kinds of stuff.

    They must be oriented properly if you look at Max's microfiche, there is mention of this also, they claim to have a "better" boot for sale, alas, it is on manufactures back order and NA. St.

  11. #26
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    Thanks, and I just re-read my last post and I see a typo....I said "it is definitely 50 years old"...
    I meant to say: "it is definitely NOT 50 years old". Guess I need my glasses changed as well.

  12. #27
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    Quote Originally Posted by STEVENRANKIN View Post
    These boots have been one of the biggest pain designs BMW did on both the twin shock bikes and the mono shock bikes.

    They do age and crack and leak. It is very rare to have a transmission seal leak, more common the boot cracks as it is exposed to all kinds of stuff.

    They must be oriented properly if you look at Max's microfiche, there is mention of this also, they claim to have a "better" boot for sale, alas, it is on manufactures back order and NA. St.

    I watched a video on Boxer 2 Valve site where the mechanic says that the "better" boot, the Siebenrock, has a grove in it which aids in the installation, especially on the paralever models, but it isn't as necessary for the dual swingarm models. I guess I am more inclined to get anything that makes installation easier, but if mine needs replacing now I may just have to use the original version.

    Update:

    I decided to get the bike on the lift as it is pouring rain, supposed to do so for a couple of more days, plus have the hurricane pass by here (east coast of Canada) on the weekend, so no driving for awhile. The adjustment bolt on one of the clamps was broken, guess the prior owner, or someone, overtightened it at some point. The boot was basically unclamped on that side, no wonder it leaked. I cleaned the boot all up rotated it a few times and it looks to be in very good shape, so will get a couple of clamps.

  13. #28
    Registered User melville's Avatar
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    Quote Originally Posted by 2wheeljunkie View Post
    I watched a video on Boxer 2 Valve site where the mechanic says that the "better" boot, the Siebenrock, has a grove in it which aids in the installation, especially on the paralever models, but it isn't as necessary for the dual swingarm models. I guess I am more inclined to get anything that makes installation easier, but if mine needs replacing now I may just have to use the original version.

    Update:

    I decided to get the bike on the lift as it is pouring rain, supposed to do so for a couple of more days, plus have the hurricane pass by here (east coast of Canada) on the weekend, so no driving for awhile. The adjustment bolt on one of the clamps was broken, guess the prior owner, or someone, overtightened it at some point. The boot was basically unclamped on that side, no wonder it leaked. I cleaned the boot all up rotated it a few times and it looks to be in very good shape, so will get a couple of clamps.
    The screw is M3 X 25mm long. If you have a good bicycle shop nearby, Campagnolo dropout screws are the right thread and should be long enough.

    My local hardware store only goes to 20mm long in M3.

  14. #29
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    Quote Originally Posted by 2wheeljunkie View Post
    The boot was basically unclamped on that side, no wonder it leaked.
    Nice that you could get #1 eyeball on the part!
    Kurt -- Forum Liaison ---> 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!

  15. #30
    Registered User STEVENRANKIN's Avatar
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    Yep

    Yep an improperly clamped boot will leak, LOL, been there had that happen. St.

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