990 Jerkyness - Or how I Un-Jerked my bike

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by DSM8, Feb 27, 2009.

  1. DSM8

    DSM8 Where fun goes to die....

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    There have been a lot of posts over the course of the last couple of years about the dreaded surging you have on the 990’s
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    Having ridden primarily Japanese and German fuel injected bikes when I got my 990 I was appalled and the lack of throttle control at slow speeds like when crawling along off road.
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    So this was the list of mods that I made to the bike, which have improved the throttle response to the point of where about 90% of the choppy on/off nature has been alleviated. I am still amazed that KTM cant get right what so many other manufactures have done but regardless, since some people are more sensitive to this issue (choppy throttle) than others this was my take on the problem and the solution that has ended working really well for me.
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    That said, these are my findings, they work for me. If you don&#8217;t like them go find your own, if you disagree fine. Do it on your own dime, I really don&#8217;t care.

    I am happy with my bike and that is all that matters&#8230;my happiness.
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    :deal
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    On to the mods.
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    • First thing I did was drop down 1 tooth on the front sprocket. Why? Because this puts the motor into its happy place a lot sooner in first gear and generally makes it more useable off road. Since this is more throttle play (RPMs) less effect from the on/off ness of it all.
      • This works for a lot of things as well and one of the cheapest performance things you can do any Kattom

    • G2 throttle cam &#8211; don&#8217;t know what it is? Do a search there are tons of threads on this. I went with the 400 cam.
    • Removed computer controlled butterfly valves in the throttle bodies.
      • You ever removed the air box cover to look at the filter, well there you are. Those throttle plates you see are computer controlled and snap shut when you roll off the throttle etc lending to what I understand as being a lean condition. What ever&#8230;.they are gone. I did notice an improvement after removal, slight but noticeable.

        Write up here: http://www.ktm950.info/how/fuel_injection/butterfly_removal.html

    • 15 minute Idle trick
      • yea it works so what wana fight about it?
      • No I don&#8217;t fully know the how or why but it does so I think it just makes the genie in the bike happy. Generally I do this if I am riding someplace that has a significant altitude change.
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    So there you have it those little things I have done which helped with my jerky throttle problems. Yes you get used to it, yes you don&#8217;t notice it (for some people), yes you can live with it as it, yes you can get a tune boy (I don&#8217;t have that kind of patience and my hat is off to those that do), yes you can get a power commander.
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    Like I said this was what I did and it works for me, got a 990 that is stock and in the LA area wanting to know if there really is a difference? Well your welcome to come on by and ride them side by side to see for yourself. I didn&#8217;t get to do that when I got mine but it would have been nice.
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    Other Mods all done prior to removing the butterfly valves which was the last mod I did
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    • Leo Vince Exhaust from the H pipe back
    • Uni Pre Filter
    • Updated FI Map back on early 08
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    My mileage is typically around 35 with mixed riding.
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    Regardless now get off the internet and go ride something already&#8230;.

    <o:p>:lol3 </o:p>
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    #1
  2. Fluffycat

    Fluffycat Been here awhile

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    Will try some of those starting with the cam. I have a SP1 or RC51 and that was bad or so i thought till i picked up a 990. How could they let it out of the factory so wrong. I use to race 2stroke 250s so i am not heavy on the gas but the 990 efi tps is way to sensitive. Thanks for the ideas.
    #2
  3. Dusty

    Dusty Long timer

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    Why not try the one that is free 1st?...
    Removed computer controlled butterfly valves in the throttle bodies.

    Then let us know how it worked for you...
    #3
  4. CHRIS_D

    CHRIS_D Been here awhile

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    Nice write up, thanks.

    The only mod I have done is the G2. IMO, I really didn't notice much of a difference with this.

    However I would like to add one that has help me a bit. I installed foam tubes used for luggage over my heated grips making the the overall grip diameter much wider. This has help to make it easier to keep a steady throttle over bumps plus the added bonus of dampening the engine vibration.

    Now because of your write up, I'm in the market for a smaller front sprocket. Anyone have one an extra one for sale? :evil
    #4
  5. Jaimoto

    Jaimoto Spaniard in Chile

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    Thanks for sharing and putting in one plece all the different mods, sure will help a lot of people.

    I did the:
    - 16 front sprocket
    - G2 throttle cam (still with the 200, will try the 300 one of these days)
    - Butterflyectomy
    - 15 min idle thing, GPR exhausts

    That removed around a lot of jerkyness, but it's still there. Know the 300 or 400 cams will help and i still have to give them try; however, the trick that takes off more jerkyness for itself, at least in my bike, is warming up the bike before the ride
    Amazing how bad my throtlle control can be when I just start it and run the bike cold.
    #5
  6. Nowwhat

    Nowwhat I'll Go Second...

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    The poor fueling is caused by the computer/o2 sensor combo...

    The above mods help...but the real fix come from a Power Comander with o2 eliminators and a tune...small price to pay to make a $12k bike run correctly...
    #6
  7. Dogtown

    Dogtown Been here awhile

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    I just learned how to twist lightly like "grasshopper". Took me about 6 months and 7000 miles! But I finally got use to it. The spinning of the rear tire while leaned over in a turn because of a heavy wrist on exit got me more then once! Hats off for the write up!!!
    #7
  8. azkiwi

    azkiwi message in a bottle

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    I've done all of the DSM8 tips above - I would declare my 990 'acceptable'. But not great.

    Is the PC plug'n'play or plug'n'pay (as in; off to the dyno)? And does it affect fuel mileage?
    #8
  9. riderbob

    riderbob Been here awhile

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    The G2 400 cam worked for me. Problem solved!
    #9
  10. Nowwhat

    Nowwhat I'll Go Second...

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    Plug'n'pay...

    The computer is trying to keep the cats happy...I paid $300 for a dyno tune...picked up some hp but the big payoff is the throttle response...

    Throttle cams, 16t etc....all help but they are covering the problem not solving it....
    #10
  11. dmage

    dmage dmage

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    Just fitted the G2 with the 400 cam - what a difference.

    I did get caught a couple of times at lights when you move the throttle a fraction expecting the usual instant power and nothing much happens - I'm getting used to it. It should be a huge difference idling through really tight stuff.
    #11
  12. CHRIS_D

    CHRIS_D Been here awhile

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    I just added the 16t sprocket. It helps around town but in the dirt it's still hard to be smooth on that throttle (to much jerkyness). The problem seems that if you roll that throttle on just a little bit there's way too much power being applied in relation to such a small movement of the throttle. If the throttle was more linear in disbursing the power it would be much smoother. When I rob the next bank I think I will buy the power commander which should ultimately fix this problem.:lol3 :lol3
    #12
  13. Nailhead

    Nailhead Inclusion Rider

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    I've done all these except the 16t & the butterfly removal, and the G2 was far and away the most effective, although the 15-minute idle made a noticeable difference.
    #13
  14. Terence FFM

    Terence FFM prof. cat-herder

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    I have a question directly (mostly) at those who have installed some sort of aftermarket controllers (PCIII, tuneboy, GPR...): does the addition of this device improve throttle response time?

    When riding the 990 at low speed/low rpm, it feels like there is a half second delay between applying throttle and the engine responding. The throttle cables are tight and the lag I am referring to is from the point the little slack there is gets taken up and the cable is under tension.

    The constant surging, while annoying, I could learn to live with but the jerky response is down right dangerous is many conditions.

    I'd really appreciate any feedback anyone can give.
    #14
  15. Grizzz4440

    Grizzz4440 Over the Hill (Wild Bill)

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    Ride a CR 500 in tight single track for awhile , you learn throttle control, + throttle tamer, you get used to it. :D
    #15
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  16. CHRIS_D

    CHRIS_D Been here awhile

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    I have a Power Commander (PC) on my FJR. It makes a heck of difference. All the Powercommander does overlay onto the top of original programed CPU setting. So for example, if the current program tells the CPU to keep the injector open for 2 ms at the 4% throttle position (tps) all the PC will do is add or subtract on to the top of this original program setting. If your PC is set to let say +1 at the 4% throttle setting it will now keep the injector open for 3 ms instead of original CPU program's of 2 ms.
    #16
  17. DSM8

    DSM8 Where fun goes to die....

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    Actually that has more to do with the profile of the throttle tube cam. This is what the G2 takes care of by making the abrupt roll on of the throttle less off the line.
    #17
  18. CHRIS_D

    CHRIS_D Been here awhile

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    The G2 with the 400 didn't do much for me.

    If we where able to look at the KTM mapping I bet you would find that they set the fuel (time the injector is on) way to rich in the lower TPS settings.
    #18
  19. foxgguy2001

    foxgguy2001 Cake

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    on another note, I found a decent profile pic of the 400 cam, and shaved my stock throttle cam to match with a dremel, and it made a heck of a difference, with no cost!
    :lol3
    #19
  20. Nowwhat

    Nowwhat I'll Go Second...

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    ding ding ding.....we have a winner....:lol3
    #20