stalling between 4500and 6000 rpm

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by norschweger, Mar 5, 2013.

  1. norschweger

    norschweger Been here awhile

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    Hello folks!
    Still trying to find the cause why my 950 stalls in the range of more or less 4500 and 6000 rpm, otherwise it runs well.
    Before I mislead you with what I think, what could you imagine or has anyone had a similar experience?
    Thanks a lot!
    #1
  2. Qwik

    Qwik Adrenaline Addict

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    Stalling implies that the engine shuts off. Hesitating is what I believe you mean. Odds are that it is a jetting issue. What modifications have you done? When did it start? Did the bike sit for a while? As much info from before and after the problem started as possible will help a LOT.
    #2
  3. norschweger

    norschweger Been here awhile

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    Thanks! I thought about it afterwards...Yes, I meant hesitate. It is a very long story.

    First I had a leaking water pump and incompetent mechanics who took my front cylinder apart instead of fixing that...Than it ran, sounding as a one-cylinder (to me, but the mechanic meant it was ok)
    Another mech blamed it on the dirty airfilter (which had about 6000km on it) and on a rubber cap that closes the airfilter box, where others have a part that I am not really sure what it is called...). He replaced the filter and took off the rubber and meant it was all good!
    Then I rode a little faster after for the first time after that the first mechanic had taken the cylinder apart and noticed hesitations.
    Back to the second mec, he did not believe it before he saw that the bike spit out quite an amount of coolant. Then he took off the carbs and cleaned them. Not sure if he set the jets any different.
    No improvement.
    After some days the valves were finally adjusted (very necessary!). Rode off to Mexico City (about 400km), problem still there. Mechanic nr.3 seemed to be a good one. We did a lot of different things, adjusted the valves AGAIN (necessary! the other guy had never done it before and did not have a lot of shims to chose from!)
    He said that the spark plugs were dry and changed the setting of the jets. Still hesitating! He said it was just because of the altitude and the bad air in MC...cause he meant that they were adjusted for an average of the whole trip (sealevel-4500m). I did not really believe this but tried to trust in him. When I got to sealevel it got even worse...

    I have tried different things but the problem remains.
    I thought it was because of a crack in the intake boot of the front cylinder. I glued it and it got better but still...I had a bad contact in the ignition lock, took it apart and sotered it twice. Not better!
    I bypassed the ignition lock with a wire and it worked fine. Then we put a switch on that point and the problem was back. Maybe it was not properly attached?
    I found a melted contact between the regulator and the main fuse, took it off and connected the cables directly, not better.
    I checked the fuel filter.
    I replaced the fuel pump with a mechanical one,did not work at all.
    I checked the spark plugs, took pics, the mechanic says they look ok...?
    I am not sure if that could have any effect but most of the screws that hold the lock of the airbox down are not working any more cause the plastic is worn and does not hold the screw any more.
    When I take off the tanks , I can see that it is quite oily in the air intake (that you have to screw out to take off the airfilter) of the front cylinder...To what degree is that normal? BTW this part has one tooth less which should hold it in place! I guess it broke off , I really hope that this part is not in the carb or in the engine!Could that cause a unregulated intake of air?
    The last time I checked the (new?) airfilter after only some hundred km it looked dirty. Same thing now after mabe 1000km ???
    I checked the fuel filter.
    Could it be some setting of the carburetor or a pinched tube?
    Maybe I should try to bypass the lock again, with a wire...
    Could the regulator have any influence?
    The battery contacts are ok on both sides.
    Could overheating or mal-lubrification (cause of water in the oil) have caused any changes (with the valves for instance) that could cause this problem?
    Is it possible that the fuel pump is starting to get bad and only works improperly in the mentioned rpm range?
    #3
  4. norschweger

    norschweger Been here awhile

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    Yesterday I bypassed the ignition lock again, cleaned different contacts, better, but still hesitating! Ii think it only does it with engaged gear. The clutch slips when the engine is cold. Could it be a connestion here?
    #4
  5. Dust Buster

    Dust Buster Been here awhile

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    Vaccumcarbs... Check the membrans.
    #5
  6. SS in Vzla.

    SS in Vzla. Totally Normal? I'm not!

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    I had the same stalling issues at aprox the same RPM... The bike ran otherwise fine.

    Turned out the front spark plug cap was not properly seated.
    #6
  7. norschweger

    norschweger Been here awhile

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    the hesitations disappear completely when I ride without the air filter (which is pretty new). Tried to adjust the jet to give it mor air and it got better but not perfect. Tried twice more...now it is spread out more over the rpm range...maybe the jet has to be bigger?
    #7
  8. norschweger

    norschweger Been here awhile

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    after a while the hesitations almost disappeared completely. Only when accelerating or slowing down there was a short gap. After getting into the jungle of chiapas it got bad again. Either the gas or the humidity...I guess it could be an eƶectrical issue that does not like humid air...
    #8
  9. norschweger

    norschweger Been here awhile

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    btw I did check the spark plugs and the fitting of the cap.
    The membrans of the carbs...hmm...tomorrow I will go to KTM Villahermosa...
    #9
  10. ABuck99

    ABuck99 0.0

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    What fuel pump are you using? Did you put the original one back on? What year is your 950 and km/mileage?
    #10
  11. norschweger

    norschweger Been here awhile

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    I think it is the stock one. Yes, I put it back.
    It is a 2006, now 59150 km on it.
    Today on the very humpy coast road towards Xcalac it sounded like a tank all of a sudden and my foot got quite warm. The gasket of the exhaust of the rear cylinder had slided out! (between muffler and the elbow). So that means that the mechanics had not put it back properly after unnecessarily taking out the engine in Queretaro. I had questioned the sound of it but they meant it was the way it should be...That also explains why it reminded me of the KLR. And I guess that also explains the hesitations. Will try to get a new one. For now I put the old one back and at least it is a little better.
    BTW: the thing that uses to be behind the airbox (to clean the air that gets out of the box or so) that I have never had, in what way does that affect the riding? The connection point was sealed with a rubber cap. The mechanics had different opinions wether that was right or stupid. The last ones were clearly against it and put a hose on instead. When I rode it without the "glove box"it was fine,only hesitating a little in first gear. When I had put back all my stuff same shit...
    I wondered if it could be a cable that gets a bad contact.
    Then it seems that it gets better sometimes after filling gas. In case of a bad fuel pump, should it not be bad permanently? Could it work in a better way just because the pressure of a full tank is higher?
    So many possibilties. Cannot wait to get that gasket...
    #11
  12. SLIV3R

    SLIV3R Adventurer

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    For me that does sound like your fuel pump might be loosing some of it pressure maybe get it tested as it could be an intermittent problem with the pump even.
    I have not experienced this myself but it from what other guys I know have said it sounds a lot like a fuel pump pressure as they do run at a high pressure and even a small amount of loss could be an issue.
    #12
  13. Mudguts

    Mudguts when in doubt GAS IT

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    950s will gravity feed fuel for about 60km to the carbs after that the the fuel pump has to push to the carbs ( so to speak )

    I rode 300km with a blown pump stopping every 60km after I bypassed the
    Pump using the left tank plumbed to carbs and the right tank I would drain fuel into a bottle and refill the left tank .

    So if you bike runs fine for about 60 km I,m guessing pump is on its way out .

    The bike will also run crap if the water pump has gone and your motor is full of water , don't rev up quick , lack of power
    #13
  14. norschweger

    norschweger Been here awhile

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    The water pump seal has been replaced only some 1000km ago.
    I just took it for a spin and it was great as far I could tell with all the pot holes (in sandals and shorts). Seems like my temporary fix with the gasket helped...we will see.
    #14
  15. norschweger

    norschweger Been here awhile

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    One day my bike sounded like a tank all of a sudden. Turned out that the gasket between the elbow and the muffler had glid out and was no longer complete.
    After an odyssee of trying to fix it I finally received a new one. Now it sounds and runs smoothly : )
    All because of mechanics not doing their job properly...
    #15
  16. tcskibike2008

    tcskibike2008 SnowHawker

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    Mechanics are to busy fixing things and not doing enough research on ADVrider.
    #16
  17. Two Moto Kiwis

    Two Moto Kiwis Homeless Somewhere

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    Dear KTM .... bla bla bla, you have gone through the ringer and back on this one mate.

    Yes but we PAY mechanics to know their stuff and NOT do shit wrong ..... we can do that ourselves :D

    At least now it is sorted. :clap
    #17