Backfire at start up....

Discussion in 'Sportster Models' started by Lang, May 22, 2011.

  1. Lang

    Lang Member

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    hello, i still cant figure this out. i sometimes get a backfire when i start my bike after its warmed up. i checked for exhaust leaks couldnt find any. no intake leaks. what else could it be. thanks

    lang
     
  2. BUBBIE

    BUBBIE Well-Known Member

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    Is it exhaust gas in the muffler? or is it a Kick back thru the intake?

    Big difference...

    Can you go into more detail?

    What is done to the bike.. List ALL Modifications..

    signed....BUBBIE
     
  3. Lang

    Lang Member

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    sounds like a big pop out of the exhaust not intake and not everytime. its a 883 with a 1250 big bore kit. screamin eagle II slip ons, twin tec adjustable ignition in the nose cone, arlen ness big sucker stage 2 a/c, andrew n4 cams, screamin eagle coil, stock heads. like i said after i drive for a bit and it gets warmed up real good and i shut it down and restart it will pop out of the exhaust. not everytime. thanks
     
  4. Hoople

    Hoople Account Removed

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    Model 1005? If so are you running single or dual fire mode. Running dual fire mode increases your chances for issues like the one you are having.
     
  5. Lang

    Lang Member

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    yes it is the 1005 and yes i am running dual fire mode. i never thought of that. i do have a single fire coil but havent installed it. maybe i will try that. it does make sense. thanks


    Lang
     
  6. ckhismine

    ckhismine Active Member

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    I have a Crane single fire on my Dyna and it made a big difference. No more pooping and cracking.
     
  7. Jack Klarich

    Jack Klarich Expert Member

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    Could be hot spots on the tops of the pistons, try some seafoam in the gas:s
     
  8. BUBBIE

    BUBBIE Well-Known Member

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    GOOD Call Hoop,,,, The single fire will Probably solve the problem...Plus not wasting a spark..
    Extra gas vapors will cause the problem especially with Duel fire set-ups on start-up..

    Been thar done that type of thing......

    signed....BUBBIE
     
  9. roach

    roach New Member

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    my evo only does it when in single fire mode and on timing setting 8 lol
     
  10. 03HD883R

    03HD883R Active Member

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    My bike used to do this for a long time, until I properly tuned it with correct jetting and setting the mixture, along with a Dyna 2ki in the nose cone.