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2014 Yamaha F250D 4stroke. Only goes up to around 3300 rpm

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  • 2014 Yamaha F250D 4stroke. Only goes up to around 3300 rpm

    Hello everyone. We ran the diagnostic software on it and there were no errors. The engine has 17 hours and started acting like this recently. We're wondering if that could be an electronic restriction of some sort, cause it acts like it. Sesnsors are not displaying any abnormalities tho.

    All 6 cillinders are working. We'll check the pressure/compression tomorrow, but I doubt that a new engine would suffer from this. I don't think there is too little fuel also, I would hear bogging because of the wrong air/fuel mixture (or am I wrong here?)

    Any suggestions on what to check? Sorry if I wasn't clear enough, english isn't my main language.

  • #2
    fuel pressures need to be monitored to make sure they stay in spec

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    • #3
      We'll check that tomorrow too, good idea. Thanks. Will update tomorrow.

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      • #4
        at key on, engine off.
        what is barometric pressure in Hg?

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        • #5
          Ok so the throttle body is not opening at full gas. (only 5mm or something). When reveraing it opens much more, not fully, but it's normal for reverse. We'll be checking the voltages now. Can we calibrate anything using the computer, or is there need of replacing the TPS?

          I provided pics of the part I'm talking about

          Last edited by Masterluka; 08-07-2014, 03:23 PM.

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          • #6
            Is it normal for this engine's TPS/servo to keep beeping (constantly ) at all times?

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            • #7
              Yes agreed, why are you fooling around with it?

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              • #8
                We are the official Yamaha dealer in our part of the country ^^. It's just the first of these engines we're doing and it's a silly problem since the diagnostics show nothing. We are calling the main dealer today if he knows if the beeeeeping noise is normal for this engine.

                When moving the throttle stick all the way back or forward the computer/motor recognizes it (100% fwd/bck), but the servo's voltage is only changed when the stick is pushed back.... The servo is also fine, when turning the motor off it does a full open and close.

                We're so close, yet so far from knowing what the problem is

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                • #9
                  CaptSolo, thanks for the suggestion, but even when the engine is not running, when I move the throttle stick all the way into reverse the the ETV (electronic throttle valve) opens as it should. But pushing it all the way forward it doesn't (LPS detects the throttle stick tho).

                  Also if it was restricted somehow we would probably see with YDIS.

                  +there is a fuel pressure sensor that would warn us if the tubing was being blocked, clogged.
                  Last edited by Masterluka; 08-08-2014, 07:38 AM.

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                  • #10
                    there are NO fuel restriction warnings.
                    the throttle is controlled by the acceleration sensor on the stbd side behind the intake runners.
                    yes it hums anytime the key is on.
                    leave it alone.
                    the ONLY fuel warning is water in the fuel detect and it only works in N.my guess is a clogged VST prefilter or a clogged VST filter.
                    hook up the fuel pressure tester and run it to the failure RPM and load.

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                    • #11
                      Rodbolt is a Yamaha Master Tech so please pay attention to what he posts

                      Sounds strange the throttle plates are not opening , but I know nothing about these new motors, so pay no attention to me.

                      You really need to post smaller pictures, Those large ones make it difficult to see and read the thread

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                      • #12
                        I don't think the throttle plate will move at key on engine off. never tried. never had a reason to try it.
                        when you turn the engine OFF.
                        now the throttle will open to full open and close to the start position.
                        that's why the start is so violent on that motor.
                        the throttle plate IS the ISC(IAC in parts of the world)
                        my guess would be the VST prefilter OR the VST filter.
                        a quick run with the fuel pressure test gauge installed will tell you.
                        however that test MUST be done at the failure RPM and load.
                        testing on the flusher will be a useless test.
                        but I will ask again.
                        what is the barometric pressure reading at key on engine off in "Hg ??????????

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