Backfire - PLEASE HELP!
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  1. #1
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    Hey guys,

    I have to say I live on this forum and every problem i have had in the past I found a solution right here.

    I have 2009 450 xc. I have Akropovic slip on, Fuel customs Air intake, R&D power pump II with adjustable leak jet, and the R&D adjustable fuel screw.

    Where i live and ride is around 3200 ft to 3800 ft. My carb came with a 40 pilot jet.

    Every time i let go of the accelerator, I get a loud backfire. My dealer suggested to put a bigger pilot jet. I started with a 42. I didn't get back fire when on Idle anymore but still get loud back fire when going down hill when i release the accelerator.

    I thought that there was an improvement so I put the 45 pilot jet and from 42 to 45 there was no improvement.

    I dont' know what to do. The bike is perfect besides that, what do you suggest???
    I want to send my carb to ranchero but wanted to fix this problem first!

    I was reading about exhaust leaks. If I would get the akropovic header, would that help???

    PLEAASE. THANKS A MILLION.

    CARL

    2009 KTM 450 XC - SX A-arms, Akropovic slip on, Fuel Customs Air intake, R&D Power pump II

  2. #2
    Junior Member Rookie
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    Exhaust leak at Haed will pop win let off with stock pipe


  3. #3
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    I don't mind spending on the Akropovic Header. Will that solve the problem? Will there be any noticeable gains with the akropovic header??

    Carl

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  5. #4
    Senior Member KTMATVHQ Addict

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    Any exhaust leak in a exhaust system can cause a back fire. It does not matter how cheap or expensive the exhaust system is. Get your current exhaust system sealed up and see what happens.
    2003 Polaris Predator / 2004 KTM 525 exc 6 speed motor.

    570 Thumper Racing kit w/ 12.5 - 1 CP piston.
    Head ported by Thumper Racing w/ new intake seats done by Pro-1 racing.
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    * #100 CDI dirt bike CDI.
    42 mm FCR carb by Walt/ Fast64ranchero. ( SX carb = No TPS )
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    Custom modded intake. Uni filter/ D2 moto adapter on a modded Predator intake tube.
    KTM Bill modded, CT racing full exhaust system.
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    Honda thumb throttle.

  6. #5
    Senior Member KTMATVHQ Guru
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    its the header leak with prettymuch all stock xc headers
    built 400 ex 461, all done up, sleeeeper. 47hp, 32lb/ft... sold

    450xc, baldwin head w/Ti valves... motoworks full system... never done...
    i may ask a lot questions, but i also know some things.
    i dont capitalize, or punctuate or use spell check, but i will joke sometimes about spellcheck

  7. #6
    Senior Member KTMATVHQ Member
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    I have the Akro header and mine still back fires sometimes but not nearly as much as it did with the stock header.
    08 XC 525

    KTM Goodies - Akrapovic - Fasst Flexx - ODI Grips - Fourwerx Bits - JD Jetting - R&D Racing - Fuel Customs

  8. #7
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    I too tried all sorts of ways to seal up the stock header, from sealants to cutting 2mm off the header. Other people on here ended up welding it. If ya can afford the AKRO header go get one ! Mine sealed up sweet, went from a 175 to 180 main jet and couldn't be happier.

  9. #8
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    Guys thank you. Just ordered the AKRO header and waiting to receive it. I will keep you posted. Anyone can give me their feeling on the power gains with the AKRO header???



  10. #9
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    I just welded up my stock headers and no more popping after that! Great 10 dollars investment..haha
    Dusty
    08 KTM 450XC
    RTR Kit
    Powermadd Hand guard
    Moose Racing Mud guard
    Front Razr 2's

  11. #10
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    i think its awesome that someone in haiti has a ktm quad. small world!!!

  12. #11
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    My Akro Header is arriving today here in Haiti. I will give you guys updates. Thanks so much for your help. Im looking forward to riding without scaring the other riders with my loud popping.. :-)

  13. #12
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    Guys,

    thank you for your help. I installed the AKRO Header and Backfire GONE!!!! Wow, what a feeling to not have to deal with that popping sound.

    Thanks again.

    Carl

  14. #13
    Senior Member KTMATVHQ Guru
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    how do u guys know that it is the header?? and where is this leak?? i too have this problem and it is very agrivating!!! it has soo much power yet sounds like crap when letting off the throttle. and i really dont want to buy a new header, im planning on running it in a stock class so no pipes allowed.
    2009 KTM 525XC #841

    Brad Mulvey Mod SX arms, SX axle, SX brake lines, KTM Big Nerfs, KTM Hood, Motoworks SR4 slip on, akro manifold, ESR heat gauge, 42mm bored carb, hrc kit, YFZ float bowl w/ adjustable leak jet, FCI "like" Intake w/ RC-5000 K&N filter.

  15. #14
    Senior Member KTMATVHQ Addict

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    Quote Originally Posted by rumlesj1 View Post
    how do u guys know that it is the header?? and where is this leak?? i too have this problem and it is very agrivating!!! it has soo much power yet sounds like crap when letting off the throttle. and i really dont want to buy a new header, im planning on running it in a stock class so no pipes allowed.
    Not trying to be a turd but, there are lots of threads on here about the problem, you can fix it by either welding the flange on the head to the pipe, or by removing the head pipe and grinding off about 1/8" of the head pipe (where the female head pipe slips over the male flange on the head. Hope that helps
    Home of Fastranchero carb Mods!!!!
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  16. #15
    Senior Member KTMATVHQ Guru
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    Quote Originally Posted by Fast64ranchero View Post
    Not trying to be a turd but, there are lots of threads on here about the problem, you can fix it by either welding the flange on the head to the pipe, or by removing the head pipe and grinding off about 1/8" of the head pipe (where the female head pipe slips over the male flange on the head. Hope that helps
    ya im new to the site and i didnt find anything off the bat thats why i asked in these threads, since they were started already, instead of me starting a new tread.

    thanks for the info though.
    2009 KTM 525XC #841

    Brad Mulvey Mod SX arms, SX axle, SX brake lines, KTM Big Nerfs, KTM Hood, Motoworks SR4 slip on, akro manifold, ESR heat gauge, 42mm bored carb, hrc kit, YFZ float bowl w/ adjustable leak jet, FCI "like" Intake w/ RC-5000 K&N filter.

  17. #16
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    I was at Daves the other day and he told me about a new titanium header flange thats about $40 bucks thats supposed to cure it. The welds are alot smaller and it seals better, or something like that. Havent found where to get it yet, was wondering if anyone on here knew...
    450XC, 12.5:1 540 kit, Baldwin Promo head, 08/06 cam, HMF Slip on, 41MM DJH carb, FCI intake, PB Oil Cooler, Eagle Eye HID


 

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