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Thread: Rough idle

  1. #1

    Rough idle

    All,
    I tried tuning the throttle bodies on my new to me R1150RT. I have done this multiple times on my GS and other oilheads I have owned, I used my twinmax and was able to adjust the idle to ~1100 rpms, balance the throttle bodies when fully warmed.
    I fired up the bike this AM and ran very rough, almost stalling even with the choke in the full on position. When the bike reached 6 bars, it ran just fine?!?

    Any suggestions on what to do next/what may cause these issues? Thanks
    Robert

  2. #2
    Has two wheels and flies hoffmanswen's Avatar
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    From my own recent experience, it could be an early indicator of an ignition problem. By balancing your throttles you've likely eliminated fuel, so fire is the next best bet.

    Since you set the throttles, I'd assume you already set the valves and inspected the plugs. How does your spark look?

    I'm not presuming to be an expert, I was just on the scene early with some food for thought.

    Good luck.
    In wine there is wisdom. In beer there is strength. In water there is bacteria. ~David Auerbach

  3. #3
    Scottish Transplant Picinisco's Avatar
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    throttle cable may need replacing
    2004 R1150GS 1978 R75G/S Frankenbike
    AMA - BMWMOA - BMWRSOC - AZBEEMERS
    Gilbert, Arizona

  4. #4
    Rally Rat
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    Quote Originally Posted by robsando View Post
    All,
    I tried tuning the throttle bodies on my new to me R1150RT. I have done this multiple times on my GS and other oilheads I have owned, I used my twinmax and was able to adjust the idle to ~1100 rpms, balance the throttle bodies when fully warmed.
    I fired up the bike this AM and ran very rough, almost stalling even with the choke in the full on position. When the bike reached 6 bars, it ran just fine?!?

    Any suggestions on what to do next/what may cause these issues? Thanks
    Robert
    Bad stick coils created this issue on my R1150RT. Replaced the first at 40k mi. the second at 44k. (should have just done both) There a bit pricey, but I found the best price at Chicago BMW. IIRC you can test by pulling the secondary plug wires at idle.

  5. #5

    follow-up

    I checked the plugs and they seem just fine. The throttle cables look decent...I may just take it to the "stealership" for a "looksie".
    Thanks

  6. #6
    Registered User ANDYVH's Avatar
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    How many miles on that RT? Could be worn throttle body shafts, especially the RH side TB. Does the bike make a "thuk, thuk, thuk" sound at idle, especially from the RH side of the bike? If so, TB shafts are worn and rattling. Also makes it difficult to balance as the TB is sucking air around the TB shaft bushings.
    Get trained! The best "performance" upgrade you can get is YOU. Visit msf-usa.org for training info.

  7. #7
    How did it run before you adjusted the synchronization? If it ran basically OK but you were tweaking it, then I suspect the tweaking.

    If it didn't run OK what were the symptoms then?

    Otherwise - go back to where you were last.
    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/

  8. #8
    Rally Rat
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    Quote Originally Posted by PGlaves View Post
    How did it run before you adjusted the synchronization? If it ran basically OK but you were tweaking it, then I suspect the tweaking.

    If it didn't run OK what were the symptoms then?

    Otherwise - go back to where you were last.
    I forgot a common issue... One of the cable ferrules became unseated at the adjuster.

  9. #9
    Bluenoser
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    My bike also runs worse when cold ( first start ) than when it warms up. Throttle sync is spot on when warm and choke off, bike idles & runs fine when warm. The difference between first start & warm bike is like night & day. Its almost like you turn a switch.I have no other bikes like mine to compare with so it is hard to explain.

    As I understand it the first generation engine management system is pretty basic on these bikes ( ie: no knock sensor etc ) so I suspect that the system has the default ( last run when warm info ) stored so that's the conditions it expects when it first starts. But conditions have changed.

    The bike runs OK on choke but does run much better when warm so I just live with it. Part of the issue is no doubt the fact that there is no real choke enrichment system on these bikes. They are designed to run very lean which creates issues when cold.

    My two cents is adjust the choke so that it will run on first start & then drive away ASAP.
    1995 R100Rt with Kenna Sidecar, 1998 VT1100T

  10. #10

    follow up

    The bike is a dual spark r1150rt-p (retired police cruiser from California) 2004 with 44K miles. I know that these service bikes are maintained regularly by BMW dealers. The bike ran rough from the get go, I replaced the little gas it had, the fuel filter and checked the plugs/cables. All seemed fine, so I concluded that the throttle bodies may be the reason for running rough.
    I was able to sync them when warmed, got it to run as it should and left alone overnight. The next morning the symptoms came back when cold and ran just fine upon warming up. This may be a cold start "gremlin" for the RT's?? I have had 4 oilheads (GS, RS, C, R) without this issue.
    I will take to the dealer and have them check it out.
    cheers

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