need advice on symptoms - too lean or rich?

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by wantok, Dec 1, 2012.

  1. wantok

    wantok Been here awhile

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    Hi people - need some advice on the following symptoms: I live in an area that is currently very hot & humid (close to sea level) My 950 ADV (2004) has stock carby jetting & 2 wings open mufflers. The hotter it gets, the worse the bike runs. It idles but has a big flat spot below about 3500 rpm, where on a steady throttle it misses a bit. It also backfires a bit on the overrun when you crank down a couple of gears. When the weather is cooler it runs better, without these symptoms. Whenever throttle opened right up, it runs fine regardless. Ive got a facet fuel pump & DNA air filter & run the bike on 98 octane.
    Do these symptoms indicate too rich or lean?
    Many Thanks

    Nick (wantok)
    #1
  2. Deepc

    Deepc Been here awhile

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    Sounds lean to me. Stock jetting with a open wings exhaust! Also, Check for the usual vacuum leaks. Also, think about installing a second fan to cool her down. I have the black dog cycle works version and it makes a big difference in traffic.
    #2
  3. Deepc

    Deepc Been here awhile

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    And pull your rear plug. It's easy to get to and it will tell you what your looking for.
    #3
  4. AdvGa

    AdvGa Long timer

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    You may want to check some of these things:

    1- Check your Battery (under a load tester)

    2- See if your Carbs are Vented with the 10" Rear, 11" Front hoses and not the Running together in the Y configuration.
    http://www.advrider.com/forums/showpost.php?p=9593998&postcount=8


    3- See if your Fuel is not Boiling -insulated Tanks
    -Have you done the Flapendectomy?
    http://www.ktm950.info/how/Orange Garage/Fuel Tanks/Flapendectomy/flapendectomy.html

    - Also Run a Fuel Treatment -like SeaFoam
    http://www.seafoamsales.com/gasoline-engine-faqs.html
    #4
  5. akarob

    akarob Green Cantern

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    Precisely. Your spark plugs will tell you what's going on. A correct mixture will show as a light tan on the plug. If it's white and kind of burnt looking, it's lean. If it's wet and dark, it's rich.
    #5
  6. StmbtDave

    StmbtDave AKA Invisible Dave

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    I would say lean. We come to Arizona for the winters to get out of the Colorado cold. It's a lower elevation and much warmer here. My 950 goes through the exact same symptoms you are having and I found simply raising the needles one notch smooths it out. Of course anything involving the carbs can't be done "simply".

    Dave
    #6
  7. MortimerSickle

    MortimerSickle Semi-Adventurer

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    Lean?

    I'm no carb man, but to me, running better when cold than when hot sounds like a rich condition.
    #7
  8. Chuckracer

    Chuckracer Jerkus Maximus

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    She's lean. Raise the needles one clip position and turn the fuel screws out to 2.5 or so...hang on tight. :deal
    #8
  9. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I think that every time I learn something about carbs, I end up knowing even less than I did before. :D
    #9
  10. wakked1

    wakked1 Aspiring Itinerant

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    Hmm, everyone seems to have missed the temperature reference. The hotter it gets the less dense the air, so the higher the fuel/air ratio gets. If it runs fine in cold temps but rough in hot, it would suggest its running rich.
    #10
  11. MortimerSickle

    MortimerSickle Semi-Adventurer

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    Not everyone.


    .
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  12. Zuber

    Zuber Zoob

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    And the answer is: rich. Cold = needs more fuel to run good. Hot = needs less fuel to run good. You need to lean it a little when it's hot out.

    Pull the carbs. Check the float levels, set them 1/2 mm lower (leaner) than stock. I remember the setting is 3.0mm from gasket surface, so set them to 3.5mm. If they are warped, one is lower that the other, then do the best you can.

    Buy and install the remote fuel screws. This allows you to set the idle-1/4 throttle mix as the conditions change. All bikes are different, some like 1.0 turns, some like 3.0 turns. These are an awesome addition.

    With the open exhaust, you only need to increase the mains slightly, go up one step only. But, this is not needed if it's really hot and humid.

    Set the throttle sensor to the correct voltage at closed throttle. I don't remember the value (0.6v?) If this is off, it can create that big flat spot at 3500 rpm.

    Are the valves in spec? It will effect the mix also. Tight = leaner, loose = richer. It's a very small change unless the valves get very tight.

    Good luck. dz
    #12
  13. Head2Wind

    Head2Wind MotorcycleMayhem

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    if stock jetting and no other modifications I would baseline verify that all of the jets are clean and float heights are set correctly. THEN test and re-jet if necessary.
    #13
  14. wantok

    wantok Been here awhile

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    This is good stuff - thanks people

    Nick (wantok) :clap
    #14