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Thread: Air Screw Adjustment and Pilot size

  1. #21

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    QUOTE (dennisfootpole @ Dec 18 2004, 09:39 PM)
    Where do you buy a new air screw if you break the plastic one? Yes, apparently I overtightened it, but it was brittle anyhow and a bit hard to turn so I just didn't know when it was seated... and if it was seated, shouldn't the motor be stalled from not enough air?

    I can't find an idle adjustment, only the airscrew on mine (where the manual shows a 2nd air screw, there is only a rivet looking nub... and the manual calls it an air screw though it seems to be a mistake, like one of them should have been an idle adjuster).

    Oh, on a 2000 250 exc

    Right now the airscrew broke in a position that sounds like about 4,000 RPM. I suppose this is not safe on my cold engine so I'm kind of in a rush to figure this out.

    Any help is appreciated.

    dennis
    band@tenfootpole.com
    805 527 1012

    dennisfootpole, you can get a air adjustment screw from your dealer that is turned by hand instead of a thin screw driver. It makes it much easier to adjust on the trail.But it is in a tight location under the carb., alot of parts in the way so you have to use one finger kind of sliding it through the parts to adjust the screw.

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  3. #22
    Lifetime Team KTMTalk scj's Avatar
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    Two stroke riders.
    If you have your idle screw in as far as it goes and your bike will not idle it's because your pilot jet is too big or the air screw is in too far. If you go to 2 1/2 turns out and it's not staying running decrease your pilot size. This will also increase the low end performance. I always try to keep the air screw between 1 and 1 1/2 turns out.

    Four stroke riders
    The low end stumble is more often than not a too rich of a squirt or the timing needs delayed just a little. A real lean needle at low rpm's get a too rich of squirt dumped into it causes the bog. The guys running a really rich pilot don't feel the bog as bad because there's too much fuel in there anyway. Of course their performance is suffering also.


    2020 Husqvarna FE501

  4. #23

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    I am looking for a little help. I have a 300exc and I found my mix screw all the way in and the bike wont Idle and has top end peformance issues. Any help here?

  5. #24
    Lifetime Team KTMTalk july3's Avatar
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    QUOTE (myosin @ Dec 10 2004, 06:39 AM)
    QUOTE (Woody @ Mar 7 2002, 11:22 AM)
    Increase and hold the idle speed at approx 1800rpm (using the Idle

    How do you know what 1800 rpm is?


    myosin,

    Get an hour meter tachometer combo. Hour meter to keep track of your service intervals and the tachometer to adjust the carburetor.

    The combo model is just a few bucks more than just the hour meter and works great. Be sure to mount it where you can see it while adjusting the carburetor. I installed mine right next to the black box on the steering stem. MUCH more accurate than the trained ear.

    I have the Hardline(?) brand and it has worked well for several years. Easy install. There are several different brands.
    2017 KTM 500 EXC-F - Rekluse Radial X clutch, LHRB, Twisted Engineering bars, Scotts Damper, Trail Tricks Suspension.

  6. #25

    Default Re: Air Screw Adjustment and Pilot size

    I am also a nub at this carb stuff and owning a KTM for that matter. I am still trying to figure this bike out and get it running correctly. Its 02 520mxc. I have the aftermarket fuel adjustment that sticks out on the carb, should this be turned out 2 1/2 turns normally? I am attempting to get it running correctly before taking the carb apart. It will start and run fine with choke on until the motor warms up then when I close the choke, it wants to sputter, backfire when I give it throttle and then quit no matter how much throttle I give. It then is very difficult to start, nearly kills the battery trying, when it starts back up it was idling really really high, I do not have a tach on the bike so I have no idea how high. I was trying to adjust the idle screw, but feel like I have it all out of wack now. I feel so dumb with this bike. Have only ridden it around the block a couple times so I do not know how it should really run, but it is fast when it will run long enough to show me. Usually about 2 mins max. lol. Any help?

  7. #26
    KTMTalk Member ktmaholic's Avatar
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    Default Re: Air Screw Adjustment and Pilot size

    Rambler. Sounds like someone put a variable accelerator pump bypass attachment on the bowl of the carb? I never had any luck with those. Do yourself a favor and either go back to stock or find instructions for the one that’s on there. Also check under the black plastic throttle cam cover to see if someone put an ‘oring’ on the accelerator pump linkage. It is not necessary on a properly tuned bike.

  8. #27
    Lifetime Team KTMTalk Old Rider's Avatar
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    Default Re: Air Screw Adjustment and Pilot size

    Quote Originally Posted by Ramblerx View Post
    I am also a nub at this carb stuff and owning a KTM for that matter. I am still trying to figure this bike out and get it running correctly. Its 02 520mxc. I have the aftermarket fuel adjustment that sticks out on the carb, should this be turned out 2 1/2 turns normally? I am attempting to get it running correctly before taking the carb apart. It will start and run fine with choke on until the motor warms up then when I close the choke, it wants to sputter, backfire when I give it throttle and then quit no matter how much throttle I give. It then is very difficult to start, nearly kills the battery trying, when it starts back up it was idling really really high, I do not have a tach on the bike so I have no idea how high. I was trying to adjust the idle screw, but feel like I have it all out of wack now. I feel so dumb with this bike. Have only ridden it around the block a couple times so I do not know how it should really run, but it is fast when it will run long enough to show me. Usually about 2 mins max. lol. Any help?
    Rambler,
    This can be caused by a plugged pilot jet.
    jet
    Old Rider
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  9. #28

    Default Re: Air Screw Adjustment and Pilot size

    Quote Originally Posted by Woody View Post
    Motocross Action Mag just had an article on how to adjust the Air
    Screw. The nice part about this method is it doesn't require you to know how the bike feels or sounds when comming off of low throttle.
    This is a big benifit to us newbies that aren't quite sure how an lean
    or rich engine sounds or feels like (i.e. we can at least get the pilot
    jetting right!)

    I just tried this method and it work very well.

    Starting with a clean filter (with the oil dried overnight) bring the
    bike up to temperature.

    Increase and hold the idle speed at approx 1800rpm (using the Idle adj.
    screw is the easiest).

    Screw in the Air screw until the engine is about to die. Slowly adjust
    the Air Screw out until you JUST reach peak rpm. If you keep turning
    the air screw out the peak rpm will not drop but you will be going
    lean.

    Once you are confident that you are just at the peak rpm point kill the
    engine and count the number of turns to close the Air screw and memorize
    this number! Turn the screw out that number, reset your idle screw and
    your done!

    Note 1) if your air screw is less than 1/2 a turn out then you should
    increase the pilot jet one size.

    Note 2) if your air screw is more than 2&1/2 turns out then you should
    drop the pilot jet one size.


    Old thread..
    It sound's great but in practice if you adjust like this, you get a lean bog... when you blip the throttle
    '06 250 yz250
    '06 250 yz250f
    '10 250 exc
    '14 250 FR
    '06 200 exc
    '16 200 exc

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