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Thread: 1990 R 100 GSPD oil leak

  1. #1
    not lost til out of gas 128521's Avatar
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    1990 R 100 GSPD oil leak

    hey all, I just replaced my alternator with an IE 600w kit. for some reason I can't get the seal on the back of the rotor to seal. it looks straight forward, the seal seems to fit, doesn't leak at idle but starts leaking when I ride it. is there a trick that I don't know? any help would be appreciated. Chuck
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  2. #2
    Registered User AntonLargiader's Avatar
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    If you haven't damaged the seal somehow, I'd be checking the rotor to make sure the sealing surface is smooth and true. I have found an aftermarket rotor that had a really awful finish on it.
    Last edited by AntonLargiader; 03-22-2018 at 05:29 PM.
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  3. #3
    not lost til out of gas 128521's Avatar
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    I test fit the seal on the back of the rotor, seems good. put some ATF on the seal prior to installation. I was going to replace the timing chain, and removed the cover to inspect. I decided the chain was ok and just replaced the tensioners. the cover seemed to go back on ok. I was reading what Snowbum says ( which gave me a headache ) He was saying something about heating the cover on reinstallation which I didn't do. it seemed to go back on ok though. I am going to get a new seal and try again today.
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  4. #4
    B Reams brook.reams's Avatar
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    Quote Originally Posted by 128521 View Post
    I test fit the seal on the back of the rotor, seems good. put some ATF on the seal prior to installation. I was going to replace the timing chain, and removed the cover to inspect. I decided the chain was ok and just replaced the tensioners. the cover seemed to go back on ok. I was reading what Snowbum says ( which gave me a headache ) He was saying something about heating the cover on reinstallation which I didn't do. it seemed to go back on ok though. I am going to get a new seal and try again today.
    The idea of reheating the cover is to ensure the nose bearing has seated all the way into the bore. You don't want the inner timing cover to be stressed, nor the bearing to have an axial load since it's a ball bearing. I have used a heat gun around the outside edge of the aluminum bearing cup after installing the inner cover and tapped the cover with a rubber mallet before tightening the bolts to ensure the nose bearing is fully seated.

    BTW, I think it's a good idea when lubricating a seal to use what it will be exposed to, in this case engine oil. That avoids any unexpected swelling due to fluid/seal material incompatibilities.

    Hope that helps.

    Best.
    Brook Reams.
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  5. #5
    Next questiuon: Was a directional seal installed correctly, or backwards?
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  6. #6
    not lost til out of gas 128521's Avatar
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    thanks for the replies, I will go out to the shop and take some pictures. I got a new seal and am going to get one of our local airhead experts to help me install it.
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  7. #7
    not lost til out of gas 128521's Avatar
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    so here are a few pictures, the first is the old rotor you can see where the seal was for the last 65,000 miles. the next is both rotors. old on bottom.
    Attached Images Attached Images
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  8. #8
    not lost til out of gas 128521's Avatar
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    here is the seal as currently installed, and the seal where I think it should ride, based on the mark on the old rotor.
    Attached Images Attached Images
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  9. #9
    not lost til out of gas 128521's Avatar
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    here is the old seal doing it's job.
    Attached Images Attached Images
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  10. #10
    not lost til out of gas 128521's Avatar
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    morning all, Anton hit the nail on the head. ( like he has done this before ) my friend Lance came by to look at my problem, a close inspection revealed the seal surface on the new rotor was rougher than a stucco bath tub, to coin a phrase. after about a half hour of wet sanding, and another half hour of polishing with fine steel wool we think the problem is fixed. the bike is back together, and as soon as the rain slows a little I will get out and test. I will post the results in a day or two.
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

  11. #11
    not lost til out of gas 128521's Avatar
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    so that was it. the seal surface on the rotor looked smooth and new, so I didn't question it. however when we compared the two, the new one felt like sandpaper compared to the old rotor. so the lesson is don't trust just because it's new. thanks for your replies.
    don't know where I'm going, but I'm making good time. 1978 R 100 S, 1990 R 100 GSPD, 2005 R 1200 GS

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