Idle Hunting?

Discussion in 'Thumpers' started by meat popsicle, May 17, 2005.

  1. meat popsicle

    meat popsicle Ignostic

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    This is on my 03 KTM 640adv. It has 5500mi on the clock. The usual mods. Valves last adjusted at 1500mi by a good mechanic. Original spark plug. The idle speed was set to aboot 1450, but I recently bumped it up to around 1500 with by adjusting the air idle screw trying to eliminate popping on decel.

    I have noticed recently that the idle speed seems to hunt around a bit. Only +/-100rpms but it does not seem stable, or as stable as I recall it used to be. It almost sounds like the engine hesitates for a bit, on a regular cycle such that the idle speed stays constant for a second or more and then wags down for a fraction of a second before returning to the idle speed.

    Does that mean anything to anyone? I was going to put a new plug in first (its time anyways) and if that didn't do it move onto the valves (it's almost time for my first time...). If anyone has any other suggestions I would appreciate it. Maybe this is entirely normal for the LC4's rpms to cyclically oscillate. :scratch
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  2. meat popsicle

    meat popsicle Ignostic

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    Maybe I shoulda added this to the end of the "hearing your valves going out of spec" thread... :lol3
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  3. creeper

    creeper Still alive...

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    Your idle is a little low Meat... reset it to 1600-1650 when the engine is fully warmed up. Chances are you low speed mixture screw adjustment is on the edge of to lean or to rich. Do you know where it is set at off the top of your head?

    Loaded's extended BST mixture screws will be done very soon. :nod
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  4. meat popsicle

    meat popsicle Ignostic

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    manual sez 1400-1500 for the idle - mebbe dey don't account for the mods? :ear

    Roger that; after I put in the new plug (it really is time...) I will try that second. Then the valves. Unless you are curious about the LS mix screw setting causing this - I could do that first. Hell, I don't even have the plug yet so I will try that first. :D

    So the wee bit 'o' idle hunting could be from the low speed mix screw adjustment? Man, y'all weren't kidding aboot the BST being sensitive to that adjustment. :arg

    :dunno the setting off the top of my head; should I run it in and back out to see how many turns?

    I have the motion pro 90deg screwdriver; not the $100 fancy one like you, just the standard $30 one. And I use it in my tool tube so it stays with me - not sure if I will need a Loaded screw (can't tell you how happy I am to say that!!! :rofl).
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  5. Loadedagain

    Loadedagain making chips

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    what if i'd like to screw you?

    creepy prototipo:

    [​IMG]
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  6. meat popsicle

    meat popsicle Ignostic

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    get in line honey.
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  7. creeper

    creeper Still alive...

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    Feck the manual.
    Naa... but if your runnin' fat or thin... especially thin, the idle is not going to be very stable. And it only counts and operating temp... if it fluctuates when cold... it don't matter none.

    Mine hunts a bit too, but chances are it's because of the FCR adjuster I still have in there.
    Loaded's BST adjuster should allow you to dial it in to the gnats ass.
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  8. meat popsicle

    meat popsicle Ignostic

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    but there's no hole :scratch

    thanks creeper! that jives with what i know about my bike's incomplete setup :lol3 gotta fire that tuner... :uhoh

    great to get some feedback on that as I was worried that maybe a valve was getting really outa spec. Its only been 4K so I should have a bit more time I hope. waiting for the torque wrenches before I start so I can do it right! :D
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  9. Loadedagain

    Loadedagain making chips

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    do not fret man... if a valve goes that far off you'll prolly hear it. as you know.... mine havent moved .... ever. and haven't had the adjuster nuts touched for about 10k so... no need to panic.
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  10. meat popsicle

    meat popsicle Ignostic

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    Just a big thanks that I forgot to add: thanks creeper - bumping up the idle, along with enrichening the air idle screw, helped stabilize it! :thumb :D

    always more to be done here (new plug going in, valve check) but that helped end the hunt for now. :wave
    #10