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Thread: K75 clutch wierdness

  1. #1
    70548
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    K75 clutch wierdness

    I'm new to this forum. First post.

    I have a 1995 K75 with only abut 25,000 miles on it. In about 1 out every 10 starts from stop, the clutch does not engage immediately. Rather, it engages gradually and is set in about 2 seconds. In most starts, it engages quite normally. Just to test, if I pop the clutch, it does make an abrubt start (most of the time). I have never felt it slip like this into any other gear, nor will it slip while in gear.

    I'm wondering what this might be. Seems far to premature and inconsistent for a clutch. I'm thinking (and hoping) something simple with the cable (which I have read is prone to failure) or perhaps a bearing.

    I'd love the input of the gear-heads on the forum before I bring it into the shop. Any thoughts?

    Thanks in advance.

    Kevin

  2. #2
    Don't forget your towel
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    Since there aren't many non-lubricated moving parts in the clutch assembly, I'd have to go with the bad cable scenario as my first (and easiest) part to trouble shoot.

    When did this slipping start? I vaguely remember someone talking about the actuating rod hanging up once in a while, I think it was a heat related issue but it was a long time ago. If the tranny was off for a spline lube right before this started something might have been reassembled improperly but the random nature of the event still makes me think a frayed cable is the culprit.

    Steve

  3. #3
    70548
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    Steve,

    Thanks for the input. Tranny hasn't been off for a while. Started a few months back.

    There is one point I didn't mention is that it does seem to happen at the same intersection, and it's the first intersection I come to when I get off the highway. That seemed just too strange to post. But perhaps the temperature is changing - heating up after being wind-blown for a while...

    I'll lube up both ends of the cable and the rod and see what happens.

    Why would a frayed cable have intermittent problems? The broken cable parts rubbing sometimes?

    Kevin

  4. #4
    Don't forget your towel
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    I was thinking a few stray wires off the cable might be hanging up on the inside of the sleeve. Very mysterious that it happens at the same place with some regularity... maybe somebody else will have a flash of inspiration.

    Steve

  5. #5
    A bozo on the bus deilenberger's Avatar
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    Re: K75 clutch wierdness

    Originally posted by kfranck
    I'm new to this forum. First post.

    I have a 1995 K75 with only abut 25,000 miles on it. In about 1 out every 10 starts from stop, the clutch does not engage immediately. Rather, it engages gradually and is set in about 2 seconds. In most starts, it engages quite normally. Just to test, if I pop the clutch, it does make an abrubt start (most of the time). I have never felt it slip like this into any other gear, nor will it slip while in gear.

    I'm wondering what this might be. Seems far to premature and inconsistent for a clutch. I'm thinking (and hoping) something simple with the cable (which I have read is prone to failure) or perhaps a bearing.

    I'd love the input of the gear-heads on the forum before I bring it into the shop. Any thoughts?

    Thanks in advance.

    Kevin
    Four possibilities, in order of likelyhood:

    1. Bad cable - disconnect the bottom end where it attaches to the clutch lever on the tranny. Try moving it. It should move effortlessly. If not - replace. Make certain BOTH ends are adequately lubed (the barrels where they go into the levers). DO NOT lube the cable itself - doing this will cause the inside nylon liner to swell up and cause binding (a lot like you describe).

    2. Binding throwout bearing housing. The throwout bearing on the K series transmissions is enclosed in a plastic cup (which is under the boot that the clutch-lever goes into.) These cups have been known to swell up and distort a bit - causing the symptom you describe. How to tell? Remove the rubber bellows/boot, and see if the cup rotates freely in the recess it sits in. Some oil leakage when the boot is off is NORMAL and expected. If it doesn't rotate freely - Fix - replace it.

    3. Binding clutch lever bearings. The clutch lever rotates on needle-bearings with basically no provision for lubing them. It is also right in front of the rear wheel - so it sees a lot of wet/road-grime/mud. The bearings have been known to fail - causing the lever to bind. To check it - while the cable is off - rotate it around it's shaft. It should move smoothly. If it feels gritty - it needs replacing. The shaft through the lever has to be removed to do this, and the old bearings pressed out of the lever. If you don't feel competant to do this - see a dealer.

    4. Bad clutch splines. K75's are prone to this due to how some of them were handled during shipping. At 25k miles - you're on the outer limits of the failure envelope (about 90% fail at 16k miles), but it's still possible. If #1, 2 or 3 isn't the cause - then it's possible that the splines are dry and starting to fail. Fix can be very expensive depending on what is found when the tranny is removed.

    HTH,
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  6. #6
    A bozo on the bus deilenberger's Avatar
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    Originally posted by kfranck
    Steve,

    Thanks for the input. Tranny hasn't been off for a while. Started a few months back.

    There is one point I didn't mention is that it does seem to happen at the same intersection, and it's the first intersection I come to when I get off the highway. That seemed just too strange to post. But perhaps the temperature is changing - heating up after being wind-blown for a while...

    I'll lube up both ends of the cable and the rod and see what happens.

    Why would a frayed cable have intermittent problems? The broken cable parts rubbing sometimes?

    Kevin
    Ah - more info. Likely to be thermally related (temperature), which makes me think the throwout bearing cup. A long highway run will lets lots of heat move backwards towards the rear of the transmission.

    I'd still check ALL of the items I mentioned.. (and how would you "lube up the rod"? It is lubricated by transmission fluid and rides inside the mainshaft of the transmission.. plus you can't remove it on a K75 from the output end of the trans.)

    Best,
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

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