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Thread: K75rt transmission

  1. #1
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    K75rt transmission

    My K75RT is getting harder to downshift into 3rd and 2nd. I must push harder to get it to shift. It does not
    grate gear teeth or anything. It just seems like it is stuck and takes effort to make it shift. This does not happen every time but happens very often. It used to shift very smooth. Anyone have any ideas as to why this just started happening?

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    Quote Originally Posted by tullypilot View Post
    My K75RT is getting harder to downshift into 3rd and 2nd. I must push harder to get it to shift. It does not
    grate gear teeth or anything. It just seems like it is stuck and takes effort to make it shift. This does not happen every time but happens very often. It used to shift very smooth. Anyone have any ideas as to why this just started happening?
    I don't claim to be an expert or anything, and I don't even own a K-bike. My son, however, does. You don't mention the year, but his was a 1987 K100 RT and the exact same thing happened about 2-3 month's ago. Per advice from others on here, they said the clutch spline needed to be lubricated. It is somewhat of a job, but can be done by average person, but you will probably need help when trying to put the transmission back on because it is heavy, awkward when you have to line up the spline which can be frustrating.

    He had checked on, and watched the videos by Chris Harris so he knew exactly what to do. He also replaced the clutch actuating rubber boot at the same time. Took us together about 6 hours of time total. That is all we did, and has worked perfectly since.

    Be sure to use a moly grease. It was recommended by one of the near-local BMW dealers (100 miles away) to purchase the moly grease sold by the Honda (mototcycle) dealer. I think it was around $8.00 per tube. 1 tube will last many years.

  3. #3
    Registered User WalterK75's Avatar
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    Sounds like clutch splines. I had the same thing. Paul Glaves has a grease he recommends for this. Maybe someone could tell us what it is. It used to be Honda Moly and Wurth SIG 3000 mixed 50/50.
    Walter

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  4. #4
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    Yep, clutch splines/tranny input shaft splines are either dry or worn. Hope that they're just dry!



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    Lee Fulton Forum Moderator
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  5. #5
    RK Ryder
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    Quote Originally Posted by tullypilot View Post
    My K75RT is getting harder to downshift into 3rd and 2nd. I must push harder to get it to shift. It does not
    grate gear teeth or anything. It just seems like it is stuck and takes effort to make it shift. This does not happen every time but happens very often. It used to shift very smooth. Anyone have any ideas as to why this just started happening?
    With my K and your symptoms it was not the splines, but rather, the clutch that needed replacing.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
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  6. #6
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    Quote Originally Posted by Paul_F View Post
    With my K and your symptoms it was not the splines, but rather, the clutch that needed replacing.
    What was wrong with the clutch? And which parts were replaced?

    By replacing the clutch disc, you are replacing the splines (or at least half of them). It is precisely the lack of lube that causes the splines on the clutch disc to wear a step in them that locks the clutch disc in the engaged position causing hard downshifts.

    Usually when the clutch splines get worn to that extent, the corresponding splines on the tranny input shaft also get worn. Replacing only the splines on the disc can result in more rapid wear to the splines than if both clutch and tranny splines were in good shape.

    Who did the work?


    Last edited by 98lee; 11-12-2013 at 04:01 AM.
    LONG MAY YOUR BRICK FLY!

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    Lee Fulton Forum Moderator
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  7. #7
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    Quote Originally Posted by Paul_F View Post
    With my K and your symptoms it was not the splines, but rather, the clutch that needed replacing.
    I think that the clutch could have some influence here - 1/2 of splines are in the plate. But, also, if the clutch doesn't completely disengage, still having some drag (which is why this is usually a spline lube as the spline will drag), and not let the clutch plate to "float" enough to disengage, it will cause hard shifting. The spline issue is usually detectable on down shifting and trying to "find" neutral when stopped.

    Another thing to check is the clutch cable. If it is getting worn, with some of the strands breaking and starting to unravel, it could cause enough drag, preventing the clutch from fully disengaging.

    In either case (clutch or just spline lube) it would take a tear down to see for sure.

    However, and I know this is not kosher, I have done something that helps temporarily. I adjust the clutch cable out so that when pulling the clutch lever it actuates the clutch plate earlier and then "pushes" it a little further along on the spline. I am aware that this is not the best fix, but it does work to get you home and to when it can be fixed properly. The danger here is that the adjustment must be done so that the clutch can be FULLY engaged when the lever is out. If the clutch isn't fully engaged, it could slip imperceptibly and cause further problems. Also, this doesn't work well if the cable is damaged as described above - and this will put more pressure on the cable, and if damaged could cause it to break completely sooner - I know as I had one do that!

  8. #8
    Curmudgeon At Large Bobmws's Avatar
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    Quote Originally Posted by jimmylee View Post
    I think that the clutch could have some influence here - 1/2 of splines are in the plate. But, also, if the clutch doesn't completely disengage, still having some drag (which is why this is usually a spline lube as the spline will drag), and not let the clutch plate to "float" enough to disengage, it will cause hard shifting. The spline issue is usually detectable on down shifting and trying to "find" neutral when stopped.

    Another thing to check is the clutch cable. If it is getting worn, with some of the strands breaking and starting to unravel, it could cause enough drag, preventing the clutch from fully disengaging.

    In either case (clutch or just spline lube) it would take a tear down to see for sure.

    However, and I know this is not kosher, I have done something that helps temporarily. I adjust the clutch cable out so that when pulling the clutch lever it actuates the clutch plate earlier and then "pushes" it a little further along on the spline. I am aware that this is not the best fix, but it does work to get you home and to when it can be fixed properly. The danger here is that the adjustment must be done so that the clutch can be FULLY engaged when the lever is out. If the clutch isn't fully engaged, it could slip imperceptibly and cause further problems. Also, this doesn't work well if the cable is damaged as described above - and this will put more pressure on the cable, and if damaged could cause it to break completely sooner - I know as I had one do that!
    And while you're discussing the cable, clean and lubricate the barrel pivot the cable attaches to in the hand lever, as well as the lever pivot.
    Bob Weis
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  9. #9
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    Quote Originally Posted by Bobmws View Post
    And while you're discussing the cable, clean and lubricate the barrel pivot the cable attaches to in the hand lever, as well as the lever pivot.
    Great advice. I learned when purchasing a used bike, that the PO hadn't done that, and I neglected to check it because there were many things that needed attention. That's what caused my cable to break! The lever/cable connection didn't get my attention until . . .well - that's the story and I am sticking to it!

  10. #10
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    Quote Originally Posted by Bobmws View Post
    And while you're discussing the cable, clean and lubricate the barrel pivot the cable attaches to in the hand lever, as well as the lever pivot.
    That is the number 1 cause of broken clutch cables. The barrel binds in the lever from lack of lube and then starts bending the cable at a sharp angle. You know what happens to metal when it is bent back and forth repeatedly.

    You notice Bob said lube the barrel NOT the cable. The cable is teflon lined and any lube tends to gum it up and cause accelerated wear.



    But the OPs problem is either dry or worn clutch splines.


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
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  11. #11
    Benchwrenching PGlaves's Avatar
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    I love these kinds of discussions. Having been into K75 clutches too many times to remember exactly I am confident this bike has dry splines. They may also be rusty. They may also be worn beyond practical re-use. Hopefully not.

    I know of a few dozen cases where these symptoms were caused by dry/rusty/worn splines. I know of one case where the problem was internal to the transmission. I know of one case where a defective rivet on the clutch disk was dragging causing these symptoms.

    The transmission needs to come out. Then the clutch disk might need to be removed but probably not. The disk friction material usually goes at least 150,000 miles and often longer than that. The splines can be destroyed in a few thousand miles if left dry. This means at least a clutch disk and probably a transmission input shaft and associated parts, pieces and labor north of $1,000.

    The last time we personally encountered difficult downshifts on Voni's K75 I pulled the transmission and cleaned and lubed the splines in a borrowed garage 1500 miles from home the next day. You put it off at your financial peril.
    Paul Glaves - "Big Bend", Texas U.S.A
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  12. #12
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    as Paul implied, you do not have much time before difficulty downshifting becomes no power to the rear wheel at all, and a more costly repair.
    from the start of symptoms, you might have a few thousand miles, at best. probably closer to 1500 than to 3000.
    Ride Safe, Ride Lots

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    Thanks

    Splines were dry. Found other problems. Transmission fluid in clutch housing found to be a leak from front trans cover. Removed cover to reseal it and the shims fell out and I did not know which we're which. I had to guess. Hope it works Rear end seal found to be leaking so had to replace it too. Boot between swing arm was split and did not notice it till reassembly so am waiting for new one to arrive. Hope it works after all that. I am a novice I hope I put it all back together right. Wish me luck

  14. #14
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    Quote Originally Posted by tullypilot View Post
    Splines were dry. Found other problems. Transmission fluid in clutch housing found to be a leak from front trans cover. Removed cover to reseal it and the shims fell out and I did not know which we're which. I had to guess. Hope it works Rear end seal found to be leaking so had to replace it too. Boot between swing arm was split and did not notice it till reassembly so am waiting for new one to arrive. Hope it works after all that. I am a novice I hope I put it all back together right. Wish me luck
    We all have our fingers crossed!!

    Were you able by hand, while transmission was still off the bike, to hand shift it through each of the gears? And...in each of the gears, could you easily rotate the input (clutch side) shaft, and have the output (driveshaft end) shaft rotate as well?

  15. #15
    RK Ryder
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    Quote Originally Posted by 98lee View Post
    What was wrong with the clutch? And which parts were replaced?

    Who did the work?
    What parts; don't remember from five summers ago. The work was done by what used to be Open Road BMW of Markham.

    I felt that the service manager was too enthusiastic with the repairs and have since had repairs done at Detroit BMW.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Treasurer of the Forest City Motorrad Club #159
    Knights of the Roundel #333

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