R1100 gs throttle body mixture screws

Discussion in 'GS Boxers' started by pizellu, Feb 23, 2013.

  1. pizellu

    pizellu Adventurer

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    Hi everyone, just bought an 1100gs, and was wondering
    How much turns should the mixture screws on the throttle bodies
    Be out? My gs is having a hard time starting, and wasn't wirking good at all.
    Furst it was back firing , then i put the screws 2 1/2 turns out and it is better now but still is stuttering when i drive it!!! Any help would be appreciated ;)
    #1
  2. mouthfulloflake

    mouthfulloflake Not afraid

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    #2
  3. slartidbartfast

    slartidbartfast Love those blue pipes

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    They are not really mixture screws.

    What do you know of the bike's history?

    I'd start by putting the screws back where they were and running a full tank of clean gas through the bike with a bottle of injector cleaner in it.

    Read up on the valve adjust and throttle-body synch procedure in the Hall of Wisdom (see link provided above or at the very bottom of the page). If you don't know the bike's history, you should plan on doing those maintenance items along with oil changes, check the air filter, change the plugs, and then see how its running. Longer term, you might think about changing the fuel filter and internal hoses in the fuel tank and cleaning the injectors.

    Mechanically, apart from normal maintenance items and a careful check of swingarm and final drive bearings, replacing the brake hoses is probably the only thing you need to consider right away.
    #3
  4. def

    def Ginger th wonder dog

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    Well, realistically, they are mixture screws in that these screws control the amount of air by-passed around the throttle plates at idle. The amount of air by-passed controls the idle air/fuel mixture and tip in throttle response. The fuel delivered at idle is considered to be constant (controlled by the Motronic) and therefore, idle mixture (and idle RPM) is adjusted by these screws. In my experience, the idle by-pass screws (BBS) have no affect on engine performance once the engine is off idle.

    Here is the reference from my REPROM (2001 GS)

    Adjust idle speed by turning the air bypass
    screws while checking that the carburettors are
    balanced.
    Idle speed: .......................................1,100 ±50 rpm


    Note the reference to carburetors. The engine is fitted with fuel injection throttle bodies not carburetors. The technical writers got it a bit incorrect.

    As for BBS initial settings, those on my model (2001) are at ~1 1/2 turns from seated.
    #4
  5. pizellu

    pizellu Adventurer

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    Well at 1 1/2 turns the bike works pretty bad, and smells of petrol! I have ordered a carb sync to tune the throttle bodies first and see how it goes. Funny thing is one day worked fine, and the day after works rubbish !!!??!
    #5
  6. Pekkavee

    Pekkavee Been here awhile

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    Have you checked the throttle cables. If the throttle cable is stuck in the right hand side it means a lot of trouble. Like this.

    [​IMG]

    Pekka
    :eek1:eek1:eek1
    #6
  7. def

    def Ginger th wonder dog

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    Have the factory sealed (blue paint) idle stop screws been disturbed on the throttle bodies?

    If so, you're going to have to start from the beginning and set your throttle bodies, possibly your throttle position sensor and your idle air bleed screws (BBSes).

    I would begin by inspecting the throttle body throats for dirt and deposits. Cledan as needed.

    Check the air filter and replace as necessary.

    Check for vacuum leaks in the intake runners and replace o-rings as needed.

    Adjust valve lash. Remove inspect and replace spark plugs as necessary.

    Report back.
    #7
  8. pizellu

    pizellu Adventurer

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    Either you're a fortune teller or I am dumb!!!!
    The cable was stuck as you said, and the bike is already feeling better. Though at 1 1/2 - 2 turns the bike works shitty!!. to get it working near to ok I had to turn 2 3/4 turns out, and also there is a huge petrol smell!!!
    #8
  9. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Wow guys, it took that long for someone to suggest the cables?:lol3

    You really need to start simple before going to the extremes. KISS!:evil

    Jim :brow
    #9
  10. def

    def Ginger th wonder dog

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    JVB, you're right. At this point in our collective careers of boxer troubleshooting, I suspect many of us just assume that the OP is aware of the unseated throttle cable thing and has determined all is well.

    But, now we still have a poorly running boxer.....

    What's next?
    #10
  11. Pekkavee

    Pekkavee Been here awhile

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    Ha haa. I did it. :rofl:rofl:rofl
    Thanks for the guy who made the picture some time ago. It is not mine.
    And I don't remember who did it.
    Sorry for using it without your permission.
    It is a very good picture.

    Pekka
    :eek1:eek1:eek1
    #11
  12. Pekkavee

    Pekkavee Been here awhile

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    Petrol smell.:hmmmmm

    You have a leak somewhere.
    Have you looked under the tank. The plate fastening the pump etc. may leak.
    Or some fuel hose connection is leaking.
    Time to change all fuel hoses maybe.
    Don't burn your bike before you find the reason.


    Pekka
    :eek1:eek1:eek1
    #12
  13. pizellu

    pizellu Adventurer

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    The smell is coming from the exhaust, i guess the bike is rich(better than me).
    #13
  14. slartidbartfast

    slartidbartfast Love those blue pipes

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    You would certainly hope that someone new to the forum would read back at least four or five threads to the last "Help, my boxer is running like crap ..." question - But if we didn't learn from the last fifty times, why should we expect any different.

    Still, I've seen a guy call for a tow truck while a dozen of his buddies stood around trying to troubleshoot his bike, when the only "problem" was that somebody had flipped the killswitch.

    If the OPs bike was running ok up until the poinit that it didn't and he (or somebody) had obviously disturbed the throttle cable, the next question becomes: What else was disturbed? If he can undo all the things that were changed, he should get it back to running ok.

    Don't know if all 1100's have rev 2.2 of the Motronic brain or whether it might have 2.4 which would benefit from resetting its memory (pull the motronic fuse or disconnect the battery for a minute). Do it anyway - can't hurt.

    I wouldn't just drop the cable back into its adjuster but would check for any other clues that something might be out of balance, such as a twisted or kinked cable or grit in the cable wheel groove on the TB.
    #14
  15. GS Addict

    GS Addict Pepperfool

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    First things first.
    Remove both screws and clean them. I suspect you will find the tips to be covered in a tar like goo.
    I use lacquer thinner to dissolve.
    Then dip a Q tip in thinner and clean the passageways thoroughly. It may take several of them before the come out clean.
    Gently blow thru with compressed air and screw the screws back in lightly oiling the O ring. Then balance the bodies.
    You many find that this solves the problem.
    #15
  16. vintagerider

    vintagerider Long timer

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    Roger04 RT fueling threads- great info there
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  17. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Did you read what the fix was?

    Jim :brow
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  18. roger 04 rt

    roger 04 rt Long timer

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    Reported fixed in post #8, back a page. Displaced cable. ;) ;) ;)
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  19. GS Addict

    GS Addict Pepperfool

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    If I had a nickel for every time................:lol3
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  20. kellymac530

    kellymac530 motorcycle addict

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    Has anyone ever tried using a dab of some kind of silicone, RTV, or something like that to just help make sure the cable stays out while doing routine maintanance?

    Something that can easily be removed and cleaned off for cable service and cleaning, but will hold the cable end in place during normal use and service?

    Just a thought.
    #20