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2003 FXDL Backfiring

Discussion in 'Motorcycle Tech Talk' started by Brian Roberts, Aug 21, 2013.

  1. Brian Roberts

    Brian Roberts Member

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    I have a 03 FXDL with stock carb, put new HD screaming eagle mufflers on, bike backfires after i let off and high RPM's , I have adjusted the Air/Fuel mixture screw out by at least 1.5 turns, idles at approx. 1000 rpm's, should i keep going? I live in Albuquerque at 5K ft. Just read something about running too lean damaging engine and am paranoid about the mixture. How do I know i have it set right.
    Brian Roberts, Aug 21, 2013
    #1
  3. Red Rider

    Red Rider Well-Known Member

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    Did you change the jetting at all? You may need to. Do you know what jets are in it, main and idle? You reduced backpressure/increased flow when you switched to the SE pipes. Is your air cleaner stock?
    Adjusting the mixture 1.5 turns may be too much, at least it seems that way. You are correct in avoiding an overly lean condition. Going too rich has different issues, as you seem to know.
    Red Rider, Aug 21, 2013
    #2
  4. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi Brian, a few things could be going on with this.
    1. Lean jetting. If still running stock jetting you need to move up one size at least on the pilot jet.
    2. Lean mixture adjustment. It is not uncommon to adjust the mixture screw out by 2-1/2 turns from seated. Try adjusting out another 1/4 turn or until there is not hesitation when blipping the throttle.
    3. Exhaust leaks. This is the #1 cause of deceleration popping (crackling). If there is a leak at either of the exhaust flange gaskets at the heads cooler air is drawn in during deceleration and causes the pop or back fire. Always change your exhaust flange gaskets whenever removing or having loosened your head pipes. I recommend the SE gaskets.
    More info on adjusting the mixture on CV carburetors.
    kenfuzed, Aug 21, 2013
    #3
  5. Brian Roberts

    Brian Roberts Member

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    I have not changed the jetting, air cleaner is stock, thanks for the advice, i'll adjust and keep ya informed. Is there a way to know if i'm running to lean? I don't want to damage the engine from running too hot, would oil temp shed any light?
    Brian Roberts, Aug 29, 2013
    #4
  6. rickslr

    rickslr Member

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    Hello Brian I have an 03 FXDL before I checked the carb and found it had a dynojet kit I was running too lean with the mixture adjustment and getting popping on decel.opened up the mixture screw and it stopped.Will be changing to a CVP kit in next couple of weeks I don't recomend a Dynojet if you take it another step and change air filter upgrade. Anyhow you could try opening up the mixture up to 3 turns from seat if that doesnt help I would tru a 48 slow jet hope that helps.
    rickslr, Aug 29, 2013
    #5
  7. chucktx

    chucktx Moderator Staff Member

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    are you using aftermarket clamps on the pipes?? if so get rid of them and use the stock harley ones....and be sure to torque them to specs. the aftermarket clamps are no good..........
    chucktx, Aug 30, 2013
    #6

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