990 Jerky throttle

Discussion in 'Dakar champion (950/990)' started by Nine90, Oct 12, 2008.

  1. Justwantoride

    Justwantoride Been here awhile

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    Thanks must have just been a snafu when I went to that site earlier. So it looks like everyone likes the 400 cam. It shows the the G2 Dirt Tamer only comes with the 400cam and is $40 less. Since I just want to go with the 400 cam I assume this Dirt Tamer is the model i want right?

    Thanks
    #61
  2. knobbyjoe

    knobbyjoe Adventure and dirt rider

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    I have the 400 on two bikes and it works for me. Others like a less aggressive cam. I think you can use the 400 and be happy. Although to be sure you probably need to test all three to feel it for yourself. I did that and did not find much difference with the less aggressive cams and went with the 400 to gain the most effect.

    Unless you find some reviews that talk about the differences for making a decision you will need to test for yourself and buy the three cams.

    I think you would be good with the 400 and save a few bucks but if you have any doubts you will need to test all three. Throttles are a personal thing. Hope that helps.
    #62
    Justwantoride likes this.
  3. gefr

    gefr Life is a trip

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    With all gathered knowledge we should conclude what makes the most difference in the jerky throttle problem. The modifications that have been tested are as follows:
    throttle cams
    fuel maps
    induction air filters + fuel maps
    removing O2 sensors
    removing SAS system

    maybe we should arrange a vote on these, or add some more
    Cheers
    #63
  4. Lloyd67

    Lloyd67 Adventurer

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    For what it's worth I have completely removed the jerky throttle on my '07 with stock airbox and exhaust by re mapping from Tune ecu, physically cutting the epc wires and switching off the o2 sensors. Maybe I just got lucky.
    As an aside, I fitted AME chicane heated grips which come with their own cam as part of the system. The throttle response is much more predictable now, possibly because there is no lateral slop anymore. Riding off road was borderline suicidal, now it's a pleasure.
    Having owned a Ducati with the worst low speed fuelling ever helped me to learn to persevere. Even when the Adventure was bad it still worked better than the Ducati ever did.
    #64
  5. rossguzzi

    rossguzzi 990 Adv.

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    I still think they need a heavier flywheel.

    I know some disagree. Thats ok. But mine fells good and strong in all regards, just a little jerky.

    Ive had Guzzi`s, some with heavy Flywheels and some with much lighter ones. It can change the feel of the motor quite a bit.
    They would still spin up quick but it would dull the snatch a bit.

    Now could a heavier one be fitted? I dont know. Zuber seems to think there is little room for adding weights. He could be completley correct.
    I would love it if he was wrong tho.
    These guys do heavier weights for many dirt bikes. http://www.steahlyoffroad.com/
    I did contact them and ran it past them. They said they would need a bike for a day or so to see if it could be done. Bit far for me to go !!

    Not had my flywheel cover off yet so cant comment on how much room there is. Again, this could be a waste of breath but I would love to see if it could work.

    I am sure it is caused by a combination of cams, mapping and too light flywheel.

    From what I have read, if it could be mapped out easerly, there would be no snatchy bikes left. Everyone would have that map by now.

    Swapping camms to I think SD ? cams and mapping is probably a better option. But more expencive.

    Adding weight to FW with your current setup could dull the snatch just enough to make it more liveable and not break the bank.

    Then again, I could be full of Sh#t
    #65
  6. DualSportSucker

    DualSportSucker El Nooberino

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    I have an '07 also which is rumored to be the worst of the 'snatchy' throttle models and I don't really have any issue with it...I experienced some jerky response and lo
    and behold, the chain was too tight... As stated earlier it's a tourquey twin with a long swing arm, drive lash is a real issue if chain tension isn't correct.
    #66
  7. rossguzzi

    rossguzzi 990 Adv.

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    I have got chain tension right. Removed rear shock(was getting rebuilt) lifted swingarm up so straight line between centre line of sprocket, swingarm pivot and rear sprocket, and made sure there was a little slack there at chains tightest point.

    Still mine has touchy on off throttle.
    #67
  8. marcoht

    marcoht n00b

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    Hey guys... Just coming around and found the flaw I was looking for. My 990 Adv (2011 in Brazil), with 60k km has just replaced fuel pump assy, TPS (short wiring) and air filter. Have the same jumpy and hyper sensitive throttle at low revs. I'm going to give "15 min idle" trick a try. I update the post after testing.
    thanks!
    #68
  9. HiOctaneOverland

    HiOctaneOverland Been here awhile

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    This topic rears its head from time to time. And it always gets into a discussion about 15minute idle, throttle tubes and a whole host of other stuff.

    The fundamental problem is the basic EFI, it’s not very refined (and KTM set up their bikes lean from the factory for emissions). The early 990’s are particularly bad, KTM got it better with the later ones but all suffer the same basic problem of surging and snatchy throttle. My 2013 EFI 500EXC has better feel and is smoother than my 990!

    So, the solution?

    Get it remapped by someone who knows what they are doing. Everything else is a sticking plaster that doesn’t fix the basic cause but just masks the symptoms. And by good remap I mean on a rolling road with a experienced tuner. You might get lucky downloading a map from the internet but all these bikes have individual quirks and a bespoke map is the best answer.
    #69
  10. pulpo2011

    pulpo2011 Adventurer

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    Marco tell us your bike setup like airbox filter, exhaust, map, O2 on/off, etc... did you replace fuel filters??
    #70
  11. Zuber

    Zuber Zoob Supporter

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    @HiOctaneOverland , you did get it mostly right. Except, KTM's are jetted RICH for emissions and this is the primary problem causing the on/off jerky throttle.

    Why? To feed the CATs with fuel and keep them lit up. If the mix was a perfect 14.7-1, very little fuel would reach them and the fire would go out.

    My testing with a wide-band O2 sensor shows 990's are crusing at 13-1 mixture. This great for power and snap, which sells bikes to a new rider. But, when you need control in those life-death, traction or die situations, it's bad. For best control, when you roll on the throttle, the engine should go from a lean (15-1) mixture and progress into a rich (13-1) mixture as more power is needed. Adding open exhaust, open air box will help a little, but not enough.

    The O2 sensors are a dumb narrow band type. They are like an on/off switch. When the perfect 14.7-1 mix is reached, or more accurately passed by, the switch is flipped. The answer these sensors are giving is 'you just missed it, now you're too lean', 'ah, just missed it now you're too rich'. So, the ECU responds by reversing and going the other direction. When you get the jerky on/off surge at cruse, or going down hill at very small throttle, or a hesitation just off idle - the O2 sensors are being looked at and the ECU is chasing its tail. Fooling the ECU with O2 eliminators will stop the on/off/on/off surge at cruse, but you still have the overly sensitive throttle problem.

    The answer is to program the fueling so that at cruse and low power the engine is close to the ideal mixture (lambda, 14.7-1). Then when the O2 sensors are looked at, very little change in the mixture is needed. When you change the throttle from on to off to on, the change is gradual.

    Look on the two TuneECU threads. I've posted several tunes on there that follow this method and fix this jerky throttle for most bikes.
    #71
    marcoht, ktmjohn, Crazygreek and 2 others like this.
  12. simon crewe

    simon crewe Adventurer

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    Well said this man!
    I had my 2007 990 remapped back in June & it feels like a completely new motorcycle. smooth and tractable dont come close. The fuel consumption is also miles better.
    I would not waste time with all the other supposed fixes - just find a good dyno shop that knows these bikes & knows what they are doing.
    #72
  13. marcoht

    marcoht n00b

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    Hey pulpo2011,

    Here it goes:
    - airbox filter: factory original
    - exhaust: factory original
    - map: not certain, but probably factory original (I'm still waiting for my TuneECU cable to arrive and check for sure)
    - O2 on/off: on
    - did you replace fuel filters?? have not replaced since last week before my post, when I had to replace full fuel pump assy.

    Also, I did the "15 min idle" trick. I've read about this here in the forum and also within the TuneECU instructions (maybe the original source??). It seems that it has improved a little. But for sure not completely.

    Another thing, I've found out that sometimes, when I release the throttle at once up to 0%, the engine reduces the bike speed strongly, while some others the behavior is smoother... Not sure if it relates to the jerky throttle issue...
    #73
  14. pulpo2011

    pulpo2011 Adventurer

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    Ok Marco, try this:
    Set TPS +/- 0,60 volts warm bike.
    With Tuneecu or KTM Dealer adjust throttle cable.

    Good Luck
    #74
  15. marcoht

    marcoht n00b

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    Thanks for the help, pulpo2011!
    As soon as I get the TuneECU cable I'll give it a try and let you know!
    Thanks again!
    #75
  16. knobbyjoe

    knobbyjoe Adventure and dirt rider

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    I don't know jack compared to Zuber. What I do know is I almost sold my 2008 990, brought new, because of the jerky throttle. Luckily I found a competent tuner and got a "dyno" tune, that fixed the problem and gave me an engine that felt right all the time especially when throttling up through the gears and going slow on rocky single track.

    Just saying I tried tune ECU and found it too difficult and others ECU tunes not right. My tuner used tuneECU and professionally got it right on the first visit. My choice and my recommendation, get a pro to tune your bike with TuneECU.

    Black Rock Playa Nevada, Burning Man site in far background.
    [​IMG]
    #76