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Thread: '12 RT redlines when started

  1. #1

    '12 RT redlines when started

    Bike is a 2012 bmw R1200RT, 75,000km. Owned by me since 3000km.
    The problem: starts right up, but revs up and bounces off rev limiter and stays there until I hit the kill switch. This just started after I had the plastics off and was monkeying around installing a new horn. Replaced an older Stebel horn, didn't change any wiring, it runs through a relay. New horn works fine. Cruise is switched off. GS911 scan no faults. The throttle opens and closes normally, but has no impact on the revs.

    The suspects: throttle cable, air leak at throttle body, electrical/ECU?
    I have removed the plastics again, removed the tank, examined the throttle cable run, opened Bowden box to confirm correct cable run in box.

    The horn went onto the OEM mount. I was in the neighbourhood of the throttle cables, but did not intentionally move, relocate or otherwise molest the cables. Are the cables sensitive to being shoved around even a little? I feel it must be a simple thing that my ham handedness has buggered up somehow, but haven't discovered it yet. Is there a way to determine proper throttle cable tension? I'm prepared to be humbled.
    2012R1200RT

  2. #2
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by doodledog View Post
    Bike is a 2012 bmw R1200RT, 75,000km. Owned by me since 3000km.
    The problem: starts right up, but revs up and bounces off rev limiter and stays there until I hit the kill switch. This just started after I had the plastics off and was monkeying around installing a new horn. Replaced an older Stebel horn, didn't change any wiring, it runs through a relay. New horn works fine. Cruise is switched off. GS911 scan no faults. The throttle opens and closes normally, but has no impact on the revs.

    The suspects: throttle cable, air leak at throttle body, electrical/ECU?
    I have removed the plastics again, removed the tank, examined the throttle cable run, opened Bowden box to confirm correct cable run in box.

    The horn went onto the OEM mount. I was in the neighbourhood of the throttle cables, but did not intentionally move, relocate or otherwise molest the cables. Are the cables sensitive to being shoved around even a little? I feel it must be a simple thing that my ham handedness has buggered up somehow, but haven't discovered it yet. Is there a way to determine proper throttle cable tension? I'm prepared to be humbled.
    While you had the plastic off again did you cycle the throttle grip and match that against the cable movement at the throttle bodies. It seems somehow you have the throttle cables caught at wide open.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  3. #3
    rabid reader dbrick's Avatar
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    I agree with Gregg. "Look where you last worked" is a useful diagnostic when things go awry.
    David Brick
    Santa Cruz CA
    2007 R1200R

  4. #4
    Registered User lkraus's Avatar
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    When that happens on my bike, it's always because I snagged the cable from the cruise control to the Bowden box while re-installing the tank. Look in the area near the radio box.
    Larry
    2006 R1200RT

  5. #5
    Quote Originally Posted by GREGFEELER View Post
    While you had the plastic off again did you cycle the throttle grip and match that against the cable movement at the throttle bodies. It seems somehow you have the throttle cables caught at wide open.
    It feels as if there is matching movement at the throttle bodies with my opening/closing the throttle. I have tried with the bars full lock to full lock and no difference. If the throttle still has full range of motion and corresponding cable movement, that makes me think it's not the throttle cable?? I'm leaning towards the cruise control cable, even though I don't think I was anywhere near it. The hunt continues.
    2012R1200RT

  6. #6
    The air has to be getting in there from some source. I would start by visually inspecting the throttle body throttle plates. Remove the air tubes and look to see if one or the other of the throttle plates are open off-idle. If so it is in all liklihood a cable issue. If not, it is almost certainly an air leak issue.

    If a throttle plate (or both) are being held open you need a total check of all cable elements until you find the problem.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  7. #7

    Got it!

    So ends the longest most frustrating horn install in motorcycling history. By process of elimination and tips from the members above, I reasoned it had to be the cabling from the cruise module. I found that there was virtually no slack in that cable, and when pushed around in a certain way I thought I could see the pulley in the splitter move a hair. I made sure the routing was unobstructed and put a turn of slack in for good measure. Success. I never would have guessed that such a small change (maybe 1 mm) could possibly foul things up like that. I've done work in that area quite a few times such as changing headlight bulbs and have certainly pushed that cable around. Many thanks to all who chipped in their collective wisdom. For me every bolt I undo leads to another bit I learn about this fabulous machine.
    I have to appreciate a characteristic of a piece of precision machinery is that by design the tolerances are very small. And yes, the cruise still works.
    2012R1200RT

  8. #8
    Registered User lkraus's Avatar
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    I'm glad you found the problem and got back to a normal idle.

    Quote Originally Posted by doodledog View Post
    ...I made sure the routing was unobstructed and put a turn of slack in for good measure. Success. I never would have guessed that such a small change (maybe 1 mm) could possibly foul things up like that...
    I think the routing was the probably the big issue, but I'd be interested to hear if you find any differences in the cruise control operation after adding the slack. Slower response, more abrupt speed changes, greater speed variance, etc.

    It's been several years but I seem to recall that I once made a similar adjustment and had an issue with the speed dropping a bit when the cruise was first engaged. Re-adjusted and now the speed remains constant. I don't remember just how large an adjustment that was.
    Larry
    2006 R1200RT

  9. #9
    Quote Originally Posted by lkraus View Post
    I'm glad you found the problem and got back to a normal idle.



    I think the routing was the probably the big issue, but I'd be interested to hear if you find any differences in the cruise control operation after adding the slack. Slower response, more abrupt speed changes, greater speed variance, etc.

    It's been several years but I seem to recall that I once made a similar adjustment and had an issue with the speed dropping a bit when the cruise was first engaged. Re-adjusted and now the speed remains constant. I don't remember just how large an adjustment that was.
    I added what I thought was a small adjustment (one turn), since obviously the system is very sensitive. On my test hop the cc worked perfectly, but need to check it out on a longer run to investigate decel/accel, resume, hills etc. I could not find a procedure for checking and correctly adjusting the cc cable in my Haynes manual or online. I'll update with my findings. It was your response of having seen this before that convinced me I was on the right track, thanks Larry.
    2012R1200RT

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