950 carb setup question

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Bonova, Mar 23, 2012.

  1. Bonova

    Bonova Adventurer

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    Hi there guys! My 1st post here so hope I'm not doing it wrong......I did a fair bit of searching but couldn't really find the answers I was looking for.
    I've got a 2004 950s With approx 70000km on.
    From what I know, the jets and needle etc are all standard, and she runs well, needs the choke to start when cold, and pops a bit on deceleration... Power delivery feels good, and fuel consumption is only just higher than my mate with a 990 when ridden together.
    She's got scorpion pipes on with no changes to the carb, and a unifilter pre filter with standard paper oem filter. These changes are only in the last 15000km......before that she was stock standard.
    I have no one near to dyno the bike, and wanted opinions please on whether the pre filter will negate the leaning effect of the performance type pipes? Bike is going in for clearances and plugs and the mechs around here not too sure on what settings to use on the needle position and airscrew. I'm at sea level.....

    Thanks!:D
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  2. Qwik

    Qwik Adrenaline Addict

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    If it is running fine then dont worry about it. But on the other hand. Spending some money with H2W for a proper jetting kit is never a bad idea. I have the same setup except a 2-1 with a remus. I raised the needls one notch and my bike runs great.
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  3. TcRulz

    TcRulz Been here awhile

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    If your using a 'Uni-filter' prefilter you will be running to rich. K2m did a lot of research using a wide band for the right 'Air to fuel' ratio. I stole his settings and they work great for me. I'm down to 142 (front) and 145 (rear) from 155/160 respectively at an altitude of 700 meters. Drilled the holes in my slides out to 3mm. Moved air cut off valve 80 to 50's position. Replaced air cut off valve 80 with a 100. Replaced 42 low speed jet with a 45. Fitted flex jet idle screws so I can adjust on the run. Put needle at 3 (K2m recommends position 2 but I found it a little flat). Made sure vent hoses are 275mm and 250mm (rear).

    I have the same Km's as you and bike runs like a raped ape and I usually get 42mpg :D.

    Flanny was running this same set up (but next size down in main jets - good enough for the guru, good enough for me).

    I hope this helps and all credit goes to K2m (legend).:clap
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  4. Bonova

    Bonova Adventurer

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    Thanks guys! It seems that the fact that the bike is running well and the pre-filter is probably counter-acting the performance pipe, means i'll just balance the carbs and leave as is (the mech can look at the plugs and assess them.
    There is no excess sooting of the pipes btw.
    I'm in south africa, so getting jet kits etc is a little more difficult :nod and to be honest, i don't have the knowledge to be fiddling too much i would probably blow the engine up :lol3 especially cause i hardly even know where all those mentioned parts are :D.
    I might raise the needles a notch and see how she runs - safer to be a bit rich i guess?
    #4
  5. thugdog

    thugdog Druid Revisionist

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    " if it ain't broken, don't fix it "



    ~
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  6. K2m

    K2m ....58....

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    These vacuum carbes are very sensitive. If it is running well..... leave it alone. :freaky

    Lifting the needle will affect the AFR's from idle to about 3/4 throttle


    That's interesting. I run the 3rd clip also I had reached these settings with the extractors that I run so I was not sure that 3 would work on yours. Your altitude would also mean a choice to leaner. This also fits in with my view to tuning set out below. This is good to know.

    I don't run a wideband when tuning a trail bike. To much trouble to set up, battery etc. When doing up my 1976 Husky 360 (It's a Mikkola replica. He won the 500 world championship 1975 on one of these :lol3 How cool is that!:D) I made some improvements as it is a rider........ and you want to have fun riding. A TLS front brake (for safety), good suspension, and an Keihin PWK 38mm Airstriker. It's very challenging to put a new carbe on a bike and start from scratch.

    I think it is a good choice when tuning to go lean as this is a noticeable condition. Sometimes it is better to know what you don't want, to know what you do want. You are one step away from perfect. Plug reading for the main jet first.

    When I go for a trail ride with the boys I leave my modern GasGas 300 at home. This thing is so good to ride......:wink: (Must be the carbon fiber cheater bits all painted grey)

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  7. pchGS

    pchGS Mark

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    Nice Rep, nice shot, remember him winning that series, IIRC he beat DeCoster?! Now back to the regular scheduled thread!

    I'd also leave it if it is not giving you a problem, I didn't be not sure I really see a difference. :huh
    #7
  8. Bonova

    Bonova Adventurer

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    Ok..... So- if I remove the pre filter ..... And raise the needle one clip to make it richer in the low to 3/4 range (ie lower clip position) then it should be as good as I can get it without a dyno tune? I will get it tested with a lambda probe thing.....just till I can tho i need an approx :wink:
    #8
  9. K2m

    K2m ....58....

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    Serious Time..........

    So the pre filter was added by the previous owner, and no changes were made to the carbs.....

    OK

    You want to remove the pre filter and lift the needle a notch (Richer)

    I would suggest you instead :- remove the prefilter and replace the #80 (pilot circuit) air leak jet with a #70. You can find the part number for this in your KTM parts manual that should have come with your bike

    There are 3 Air leak jets in each carb. They are found by removing the plastic cover that fits between the air filter and the carb.

    Changing the mufflers has little to no effect on these CV carbes so no changing for these.
    #9
  10. Bonova

    Bonova Adventurer

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    Thank you K2M.
    I will remove the prefilter and leave the needles as is.
    Sorry - one more question tho - so the mufflers make little difference - that's good to hear.
    What am i doing by changing the pilot air leak jet to a # 70 ?

    Thank you very much for your help with the stupid noob questions!
    #10
  11. K2m

    K2m ....58....

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    I did not know what they were either. One of the inmates, Autostream said something years ago, in the early days before we discovered the tricks to tuning CV carbs. I had been using programmable management systems to run cars..... Auto said something and bingo I knew what the equivalent computer function was............. So When you grab some throttle you need the amount of gas that jet can provide........ but as the engine catches up....... it requires less fuel...... the "Load" lessens and this is what a "leak" does, it leaks air behind the jet lessening the fuel supplied to the engine.

    In standard form these bikes have a fuel delay when steady cruising. Most people make the mistake of lifting the needle, which does fix the problem, but creates other problems.

    I think that this is the best solution to this problem, but all my work was with a prefilter as that is the superior set up. These carbes benefit from a bit more restriction in the air tract. The slide will react quicker giving a feeling of more power. The only real solution is fitting FCR's.... quicker throttle response, better breathing, But forget river crossings :lol3

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    I don't think this will work !!!!!! :huh


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  12. Gustavo.Ramos

    Gustavo.Ramos Been here awhile

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    NOOOOO!!!! :cry
    #12
  13. K2m

    K2m ....58....

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    Actually there is no real reason that one could not be adapted. Inmate Dustobust made one. using the old air box as a template you can make a base. the rest is easy enough. You could go through water say up to your knees as they are without an airbox,, but I would not try anything deeper. You have got me thinking tho...... I better make something up to fit for touring :1drink

    For normal street use I love the Ducati look of naked carbes.....

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    I could build up from this base something to lay flat on the top of the frame
    tubes so that when I bring the tank down on top it closes it off. 'll need to put a "flat" across the back of the tank to seal...... It's good to have thought of this before glassing/finishing the tank, which is lucky as I was going to do it 3 days ago. Build a snorkel at the front...... to the workshop :freaky

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  14. K2m

    K2m ....58....

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    I could reopen the tank and build a tube to the top of the filters....... Fuuuukkkkk how high would the breathing be and it solves another problem....... I luv the roar of FCR's. The new tank was going to stop that.................. Maybe a bit of flexitube to the faring..... no I won't hear them....... It's good to be mad :lol3 Big thanks

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    Run the tube from behind the filler to the middle of the filter area...... Minimal loss of fuel......... So how big should it be ?????

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    #14
  15. K2m

    K2m ....58....

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    OK you win................. Big thanks :freaky

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    The faring will catch the air and force it in. I like this as something to copy

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