Shooting flames with my GS muffler

Discussion in 'GS Boxers' started by GB, Aug 1, 2007.

  1. GB

    GB . Administrator

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    I'm riding along happily today, the bike is running great, all of a sudden, I notice the bike is idling at 2000 RPM.. hmmm... odd... A minute or two later, I pull up to a stop sign, pull in the clutch and the bike stalls. Hit the starter, it starts, but unless I keep the revs up, it stalls.

    Well, this is going to be an interesting ride back to my dealer. I kept it running with very few stalls, until I was within a short distance to the dealership, when I noticed the bike is sputtering and the exhaust is making weird popping sounds while idling at a traffic light. I look back to see flames a foot long shooting out of my exhaust pipe!! :yikes It did look kinda cool. :lol3

    The dealer takes me right in, hooks up the bike to the computer and determines that the TPS (throttle potentiometer) is dead. It is quickly replaced and all 4 spark plugs which were badly fouled were also replaced and I'm back on the road again... :thumb

    So, TPS failure symptoms:

    initally, an increased idle speed
    stalls when in neutral, or clutch engaged
    hesitation while riding at cruising speed, as though there's a starvation of fuel, and lastly, shooting flames (from the unburned fuel) from your exhaust.

    Today, the TPS is on backorder, so one was removed from a bike on the showroom floor.
    #1
  2. configurationspace

    configurationspace delooper

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    Do you have a catalytic converter on your bike? I'm guessing not.
    #2
  3. Beeming

    Beeming Itchy Feet

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    Flames eh :D Kewl. Thanks for the low down Chief. Your dealer sounds like they have a finger on the pulse and very helpful. Is that faulty censor a common fault with our bikes? Worth carrying a spare one?

    Cheers

    Tads
    #3
  4. GB

    GB . Administrator

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    yup, I do. dealer explains that the TPS malfunction thinks the throttle is open to full, and is dumping more fuel than can be burned in the cylinder.. :dunno
    #4
  5. GB

    GB . Administrator

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    I don't recall reading anyone writing in about a bad TPS. I also don't think you can just remove it (easy, 2 screws, and a quick disconnect wiring harness) and install one yourself. There's some way it has to be set to operate correctly. The head mechanic said people play with it and come in to say the bike isn't running properly. His advice: don't touch it.

    I wouldn't think it's worth carrying a spare.
    #5
  6. blazer

    blazer Vote Blazer for President

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    I have heard of this happening to two other guys. Both bikes were completely dead and non-repairable within 200 miles.

    One of them is dead.

    You're screwed.

    B-
    #6
  7. dronning

    dronning TNT -The Naked Truth

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    I replaced mine myself ('06) the adjustment is done with the ignition on & before starting by doing 2 full opens of the throttle. It's just 2 screws to mount it and they have no position (slots) adjustment unlike the previous versions.

    Dave
    #7
  8. Sgt Rock

    Sgt Rock Adventurer

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    Thanks for the helpful info. Me being new to the GS world it's definately something to keep in mind
    #8
  9. NLS

    NLS My bike needs washing...

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    so cat converter survived this? (or you are just given a good reason to change pipes?)
    #9
  10. RL Lemke

    RL Lemke Long timer

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    Reading the title, I thought that this thread was going to be about a new accessory allowing us to throw flames like the low rider cars.
    #10
  11. Spike

    Spike Time Traveller

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  12. GB

    GB . Administrator

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    I hope so.. bike is running fine now..

    Flaming asshats behind me would be a nice trick though!! :lol3
    #12
  13. McKanna

    McKanna Cleanconscience=Bad Memor

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    The TPS (throttle position sensor) is a sensor located on the left throttle body which tells the Motronic the relative position of the butterfly trhottle plate that regulates de air intake, this allows the Motronic to calculate the adequate amount of fuel needed to achieve the 14:1 air/fuel ratio.

    What the dealer computer reads it is basically the voltage at pin #1. If you pull down the rubber cap from the electrical connector on the sensor you will notice 4 wires. The wire closest to the rear (number 1 – red/white) is effected
    by throttle openings up to 1/8th turn. Baseline Voltage must be between .370 and .400 vdc. An incorrects TPS setting is tipically the cause of poor response, backfiring and surging.

    It has been said that motorcycles operated at high altitude (4000 feet or more above sea level) benefit from settings closer to .370 and bikes operated at sea level should be adjusted closer to .400 vdc.

    I live at 5000 ft. in Guatemala City and adjusted mine to .385 and it works great.

    This adjustment asumes that the throttle cables are properly adjusted and the engine has been properly synchronized.

    McKanna
    #13
  14. GB

    GB . Administrator

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    McKanna: I failed to mention that my bike is a 12GS, I don't think the TPS on it is adjustable like the one on your 1150 :dunno
    #14
  15. def

    def Ginger th wonder dog

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    TPS sensors rarely fail. Riding through water could bring on problems if the TPS is wetted or submerged.

    Older boxers must have the new TPS adjusted and set using either a VOM (a DVOM works best) or the Motronic computer thingy at the dealer. Newer boxers, bolt on the new one and ride.

    When the TPS is changed or adjusted, I would recommend new plugs be installed and the new plugs read after a tank of fuel.
    #15
  16. GB

    GB . Administrator

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    Hmm... :scratch, the dealer did wash the bike a bit too vigorously and had it detailed.. and the tech was complaining about finding water near the secondary plug, under the jug.. hmm... interesting coincidence

    Thanks for your input. The tech did say that the new TPS doesn't need to be set, it "learns" and sets the idle on its own. :dunno
    #16