F560 GS '04 Twin Spk - Wont rev over 4K

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Thread: F560 GS '04 Twin Spk - Wont rev over 4K

  1. #1
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    May 2020
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    Default F560 GS '04 Twin Spk - Wont rev over 4K

    This fault has just cropped up - any help greatfully accepted......
    Quite simply the motor will not rev over 4k rpm in any gear.
    You can pursuade it a tad higher, but only a few revs worth. Get to 4000 rpm and Durrrrrrrrrr! complete loss of power. Screw up the throttle to max -nothing.
    Drop or ease the throttle at the 4k mark and it picks up just fine until it hits the 4k mark again.

    This is coupled with an inability to drop to idle rpm correctly - as the revs fall off too the bottom end of the rev range, the motor stalls. Its a case of de-clutching early and keeping the revs over 2K. Rideable - but not much fun!! Limited to 60mph in top and stalls at every junction!!
    HELP!
    I am a competent mechanic - built and raced my own road-race sidecar outfit, so happy with any technical talk!

  2. #2
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    The first thing I would do is a diagnostic test and check for fault codes - with a bit of luck the ECU/BMS will tell you what is happening
    2006 F650GS in Black
    9,300 Miles

  3. #3
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    02 dakar
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    Dec 2019
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    Agree with ecu sounds like it's gone into some sort of safety, limp mode. If not coil test or fuel pump also worth a look.

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  5. #4
    Bike
    GS/Gd Dakar 2003
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    couple of basic checks, which you have probably done already:
    Battery terminals not loosened ? Causes also sorts of issues, can start ok
    wiring/connectors around ignition switch, damp/corrosion ?
    Fuel contamination, refuelled recently? Filler cap vent not blocked?
    Ignition/plug leads loose/corroded,

    Fault code reader should pin point issue, rare,but not unheard of for ECU to fail,
    let us know how you get on
    2003 GS Dakar
    BMW Panniers, top box, tank bag
    + loads TT stuff that came with it!

  6. #5
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    It will be interesting to see whether there are any helpful fault codes logged. Otherwise it can be very tricky to diagnose the cause of problems with fuel injected engines. As said, it could be due to a simple electrical or fuel supply issue but, if not, might be due to a coil problem, a fault with the O2 sensor or even the injector which, unfortunately, can sometimes only be ruled out by substitution with a known working unit.
    2006 F650GS in Black
    9,300 Miles

  7. #6
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    Hi folks – well its ‘job–jobbed’ and a big thanks for all you guys who responded.
    As the motor performed ok up to 4k, thoughts were ‘I have a fuelling issue’.


    First thing to look at after the plastic was off was any signs of loose wires/connectors etc around the transducers that input to the ECU.
    Note: a large number of fuel injection snags can be cured by just cycling the connectors from these transducers. The garage bloke says ..... “It was yer crankshaft position sensor guv”. Odds are that by just removing the connector then replacing it sorted the snag, and a new transducer was not needed at all.
    With everything in plain sight it’s easy to remove the ECU, firstly just cycle its connector. However the fault was instantly apparent. Removing the plug and looking down into the connector receptacle on the ECU, there was a whole load of water and associated gunge. The rearmost sets of pins were all surrounded with water.
    As the item is well shielded and part of a goodly substantial plug/socket arrangement I can’t see how water got in there in the first place.
    Both plug assembly and the ECU pin set were cleaned and dried plus a touch of WD40. Reassemble and try. Nothing at all – key clue - the fuel pump was not running ( that 2 sec burst you get at ign on).
    Off with the ECU again for another look – my 78yo eyes eventually spotted that the LH pin on the rear row of pins looked wrong. Looking at the plug side, the corresponding pin receptacle looked very bad. In fact the tiny receptacle was hugely corroded and had fractured. The fault was most defiantly staring me in the face.
    Now for a fix, no chance of buying a receptacle to replace the knackered item, where would you look even to find one to buy?
    On with the ‘bodgers’ hat, I took a 40mm length of 1mm i/d brass tube, 5mm up from one end, I wasted the tube to enable me to fill the end with solder. The relevant pin on the ECU was tinned and the tubing soldered to the ECU pin. On the plug body good old ‘Mr Dremel’ ran a 2.5mm drill bit through the plug body removing all the rubbish from the corroded original receptacle. The plug was offered up to the ECU and my brass tube protruded thru the top. The little rubber gubbins was taken off the existing lead and pushed down over the tube to seal the hole. The lead was then cut tinned and soldered to the tube. ECU secure – Battery connected - Ign on – two lots of throttle twist – hit the button.
    Bingo! A smooth regular idle at the 1500 rpm mark – rev’ed cleanly to 5K – dropped back to a steady 1.5k
    Comments: How the heck did the ECU Plg/Skt Assy, come to be water contaminated? True it was parked outside without a cover during the March/April rains. However by the look of the corrosion and crap in the receptacle body it indicated a long time contamination. Even with the water surrounding a whole set of pins the ECU did not cry ‘Uncle’ - so well done Motronic(?)
    If you own a Twin Spark and it plays up like mine – make your first stop the ECU.

  8. #7
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    Well done for sorting the problem - it would have been interesting to have seen what the ECU was actually reporting in the way of any fault codes

    In terms of how the corrosion might have happened, I don't think the F650GS wiring harness and electronic devices are that well shielded from the elements. Another forum member had all sorts of electrical issues a few months ago and, having looked at the bike with him, I came to the conclusion that it was mucky water that had got under the false tank and into the electrics that caused the issues. A regular liberal application of WD-40 on the electrics would probably help prevent these types of electrical problem.
    2006 F650GS in Black
    9,300 Miles


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