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Thread: Throttle position sensor

  1. #1

    Throttle position sensor

    Greeting. New member with 2002 F650GS Dakar project bike (bought cheap, needs some work). I'm working my way through a problem I have researched quite a bit: the dreaded surge, stall, and a tachometer that goes to redline while then engine maintains constant speed. The current item on the checklist is the throttle position sensor. I checked it with an ohm meter and the positions at idle and full open seem correct (closed circuit). Physically, however, it is questionable. I do not hear any mechanical noises when adjusting it off the bike. As I roll out of idle, should there be an audible click of the idle switch opening? if that switch is broken, that might explain the erratic rpms while idling. Has anyone taken one apart? Since this is a budget project and I'm trying to stay lean, I wanted to reach out before spending $130 on a new one. Thanks for the assist. And if there is an existing thread on this, by all means show me the way...

  2. #2
    Liaison 20774's Avatar
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    Welcome to the forum! There are a few ways to browse around for potential past info on this.

    - the Tag Cloud -- at the bottom of the screen are a number of Tags for this Thread that were entered by a member. One is Throttle Position Sensor that is clickable for past threads that also have this as a tag. You can do additional search in the cloud by clicking on View Tag Cloud.

    - the Similar Threads pane at the bottom of the screen -- this is generated by the forum software and provides what it thinks are similar threads based upon titles.

    - Google site search -- go to google and type something like "site:forums.bmwmoa.org F650GS throttle position sensor" (no quotes) into the search box. Try other search items that might be specific to your issue.

    Good luck!
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  3. #3
    Registered User wkoppa's Avatar
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    Quote Originally Posted by jbwebb650 View Post
    Greeting. New member with 2002 F650GS Dakar project bike (bought cheap, needs some work). I'm working my way through a problem I have researched quite a bit: the dreaded surge, stall, and a tachometer that goes to redline while then engine maintains constant speed. The current item on the checklist is the throttle position sensor. I checked it with an ohm meter and the positions at idle and full open seem correct (closed circuit). Physically, however, it is questionable. I do not hear any mechanical noises when adjusting it off the bike. As I roll out of idle, should there be an audible click of the idle switch opening? if that switch is broken, that might explain the erratic rpms while idling. Has anyone taken one apart? Since this is a budget project and I'm trying to stay lean, I wanted to reach out before spending $130 on a new one. Thanks for the assist. And if there is an existing thread on this, by all means show me the way...
    I had that problem with a 2013 650 GS. Swapped a lot of stuff like the ECU and stuff. Problem finally went away when I replaced the fuel pump (not the fuel pump carrier) with a cheap $20.00 fuel pump from e-bay. Nobody could figure out why. Tach goes to red line without revs going up, bike quits (pretty exciting when your passing a semi on a two lane when traffic appears ahead).

    Wayne Koppa
    Grayling, MI
    #71,449

  4. #4
    Thanks. I have a new fuel pump, same one you mentioned most likely, and will try that soon.

    The TPS is a potentiometer, so there is no micro-switch to create a "click". My previous Ohm readings don't really help out there. I am having trouble finding any reference to the min/max resistance for the sensor, so I cant tell is it good or bad.

  5. #5
    MOA #24991 Pauls1150's Avatar
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    The Bosch spec sheet for my 1150 (and no I don't know if yours is the same) says -
    1) the resistance between terminals 1 and 2 is 2K ohms +/- 20%;
    2) when the wiper is sitting at "zero", the resistance between terminals 2 and 3 should be between 710 and 1380 ohms.
    Sorry I couldn't upload the PDF.

    Per member DieselYoda: This sensor's [1100-1150 bikes] Bosch part number (NOT the "BMW" #) crosses to everything from a 1987 Ford Pickup to a Volvo D11 Exhaust Brake Angle Sensor.

    And as far as taking one apart, yes I did...
    P7040003.JPG

  6. #6

    Problem solved

    Good news - problem solved, Bad news - I did not follow the scientific method...

    Although my battery tested fine for voltage and CCA, I bought a new one based upon the various threads suggesting how sensitive these bikes are to batteries.

    I received a new TPS and compared it with the old one. The resistance was different between the two. New range between left contact and common was .8 to 5.3 ohm, idle to full open throttle. Old TPS read 1.5 to 8.9. Although there is a difference, I could not say if it is significant enough to cause my issue. Since I replaced the TPS and battery at the same time, I''m not sure if one, the other, or the combination solved the issue. Honestly right now I dont care. The bike runs great and I just want to ride.

  7. #7
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Nice
    Thanks for following up for us.
    Welcome to the forum!
    Gary
    "You can do good or you can do well. Sooner or later they make you choose." MI5
    Mod Squad
    2009 F800GS 1994 TW200

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