Subtle release of the throttle, bike suddenly goes to engine breaking mode



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Thread: Subtle release of the throttle, bike suddenly goes to engine breaking mode

  1. #1

    Subtle release of the throttle, bike suddenly goes to engine breaking mode

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    Hello,

    My first post.

    I have a question about a slight problem that my bike has been experiencing over the past 2 years.

    I own a '07 Suzuki GSF 650. I had it since new. I put about 24k on it - I've had my M license for over a decade. I don't ride as much as I used to; being a dad had something to do with it. Anyway, I still ride over the summer every once in a while. But lately (and it never did this before) any subtle release of the throttle (and I mean subtle), the bike suddenly goes into engine breaking mode. Its not a great experience for a passenger because they suddenly slide forward into the driver. Not a great experience for the driver either. I can understand that scenario if I completely let go of the throttle and went into full engine breaking mode. Knowing that I am about to fully let go, I am well prepared for it; its not something I would do on a regular basis to begin with. But on a subtle release, it is not normal for the bike to re-act the way it would with a full release.

    Has anyone experienced this type of situation before?

    I am not sure how else to explain the situation. I tried to explain it to a mechanic once...didn't go well. Anyway, I have been reading online about possible symptoms of a bad throttle position sensors, bad ECM or even cable issues.

    It sounds like it could be something of that nature but not sure. Before I venture into buying parts and spending money, I just wanted to check if others may have had similar issues with older bikes.

    Cheers,
    Bob
    Last edited by CanadianBob; 03-12-2018 at 05:32 PM.

  2. #2

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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by CanadianBob View Post

    I am not sure how else to explain the situation. I tried to explain it to a mechanic once...didn't go well. Anyway, I have been reading online about possible symptoms of a bad throttle position sensors, bad ECM or even cable issues.
    Welcome to the mess!

    Do carbureted bikes even have a throttle position sensor? I thought that was an EFI thing.

  3. #3
    TwistedKestrel's Avatar
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    A 2007 GSF 650 is EFI.

    Terrible off-throttle manners is a hallmark of earlier bike EFI systems, but your description makes it seem worse than I would expect. Wouldn't hurt to start with checking slack & stiction on the throttle and return cables
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  4. #4

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    My suspicions would be the throttle position sensor, but without a service manual in front of you to give the static resistance readings (if available) it would be pretty hard to tell.
    Fortunately its sold separately, not as part of the fuel injector assembly (part # 13580-18H00) and runs about $100 if that proves to be the problem.

  5. #5

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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by TwistedKestrel View Post
    A 2007 GSF 650 is EFI.

    Terrible off-throttle manners is a hallmark of earlier bike EFI systems, but your description makes it seem worse than I would expect. Wouldn't hurt to start with checking slack & stiction on the throttle and return cables
    My bad...carry on.

  6. #6

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by TK4 View Post
    My suspicions would be the throttle position sensor, but without a service manual in front of you to give the static resistance readings (if available) it would be pretty hard to tell.
    Fortunately its sold separately, not as part of the fuel injector assembly (part # 13580-18H00) and runs about $100 if that proves to be the problem.
    I purchased a service manual which goes over (at a high level) how to test for readings of the ECM and TPS. I may need to watch a few you tube videos before I attempt it myself.

    Thanks for the part #, that saves me time!

  7. #7
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Welcome ....start with the throttle cable - might be out of adjustment or just out of lube so you close it a bit then it unsticks and it closes sooner.
    Beyond that - others can help more.

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  8. #8

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by TK4 View Post
    My suspicions would be the throttle position sensor, but without a service manual in front of you to give the static resistance readings (if available) it would be pretty hard to tell.
    Fortunately its sold separately, not as part of the fuel injector assembly (part # 13580-18H00) and runs about $100 if that proves to be the problem.
    Throttle position sensors are typically pretty simple.
    Two or three wires in: One is 5 volt, one is ground, one is signal. If there is only two wires it grounds through the frame (that's bad engineering, but it's done all the time).

    Find the TPS. Leave it connected.
    Find 5 volt (VCC).
    Find ground (usually black).
    Test the voltage from signal to sensor ground as you twist the throttle. Should read near zero, but not zero, closed and near 5 volts fully open. The voltage should increase/decrease in a linear proportion.

    To test the senor in your hand: test impedance from signal to 5 volt (VCC); starts high, but not infinite, and goes low as it opens.


    ...and there's lots of carbs with a TPS.

  9. #9
    Riceburner's Avatar
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    My carbed bikes have TPS.

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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by Owen View Post
    Welcome to the mess!

    Do carbureted bikes even have a throttle position sensor? I thought that was an EFI thing.
    Yes there are carbed bikes with TPS sensors.
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  11. #11
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Are you sure there isn't a brake dragging or something else chassis wise binding up? There's a good chance you wouldn't notice it under power and what you describe seems a little aggressive for any kind of engine braking.

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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by Riceburner View Post
    My carbed bikes have TPS.
    Quote Originally Posted by N3WMAN View Post
    Yes there are carbed bikes with TPS sensors.
    Hmm. Learn something every day. I've had 3 carb bikes and no TPS sensor that I know of. Thought they just have push/pull cables.

  13. #13
    TwistedKestrel's Avatar
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    It's generally a early-mid 2000's thing, the TPS is used to help control ignition timing. My GS500 had it (along with 3 jet carbs), I think ZRX1200s had it, Bandit 1200s, etc
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  14. #14

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    I had new break lines put on a year ago. I don’t believe its dragging brakes; but it’s something I guess I can’t rule out at this point.

  15. #15
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Sounds like it could just be a dirty fuel system. Fuel that sits a long time between rides can gum up injectors, tps and other components. If nothing else changed prior to this sudden issue I'd run some seafoam or other fuel system cleaner through it before checking anything else.

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  16. #16
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by blackcamaro View Post
    Are you sure there isn't a brake dragging or something else chassis wise binding up? There's a good chance you wouldn't notice it under power and what you describe seems a little aggressive for any kind of engine braking.
    agree this is worth looking into
    also a chain that's zinging tight

  17. #17

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    It's too bad we didn't have a technical section on this forum.

  18. #18
    Skyway6's Avatar
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    glad i do not own a Suzuki. Would not want a bike that has a mode that breaks your engine.
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    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by Skyway6 View Post
    glad i do not own a Suzuki. Would not want a bike that has a mode that breaks your engine.
    Funny..

    Quote Originally Posted by CanadianBob View Post
    Hello,

    My first post.

    I have a question about a slight problem that my bike has been experiencing over the past 2 years.

    I own a '07 Suzuki GSF 650. I had it since new. I put about 24k on it - I've had my M license for over a decade. I don't ride as much as I used to; being a dad had something to do with it. Anyway, I still ride over the summer every once in a while. But lately (and it never did this before) any subtle release of the throttle (and I mean subtle), the bike suddenly goes into engine breaking mode. Its not a great experience for a passenger because they suddenly slide forward into the driver. Not a great experience for the driver either. I can understand that scenario if I completely let go of the throttle and went into full engine breaking mode. Knowing that I am about to fully let go, I am well prepared for it; its not something I would do on a regular basis to begin with. But on a subtle release, it is not normal for the bike to re-act the way it would with a full release.

    Has anyone experienced this type of situation before?

    I am not sure how else to explain the situation. I tried to explain it to a mechanic once...didn't go well. Anyway, I have been reading online about possible symptoms of a bad throttle position sensors, bad ECM or even cable issues.

    It sounds like it could be something of that nature but not sure. Before I venture into buying parts and spending money, I just wanted to check if others may have had similar issues with older bikes.

    Cheers,
    Bob
    Simple stuff first:
    1. Regular maintenance? Was the 21K-ish service completed? Plugs, air filter, coolant... How many total kilometers on the bike?
    2. Have you made any changes to the bike? Air box mods, slip-on, air filter changes, electrical accessories...
    3. Tires, brakes, chain and sprocket condition.
    4. Once you are certain it is not something simple, then you can move on to the more complicated electrical problems.

    Don't throw parts at the problem, find the issue and fix it.

  20. #20

    Re: Subtle release of the throttle, bike suddenly goes to engine breaking mode

    Quote Originally Posted by Skyway6 View Post
    glad i do not own a Suzuki. Would not want a bike that has a mode that breaks your engine.
    I agree!

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