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2009 kx250f popping bad on decel

Discussion in 'Fuel' started by pimpit_r6, May 26, 2014.

  1. pimpit_r6

    pimpit_r6 PR Member

    Location:
    Ellsworth, OH
    I jetted plenty of carbs before but this one has me dumb founded. The current jetting is 178 main, 45 pilot, needle 4th clip, fuel screw 2 1/4 turn . Hot start is not stuck or engaged, Checked exhaust gasket ring and its fine. No carb leaks anywhere. Any suggestions appreciated. Carb is currently off bike, Waiting for fuel screw to arrive tomorrow.
     
  2. SCHAFFERNOCKER

    SCHAFFERNOCKER PR Addict

    Location:
    Canton Ohio
    Racing Number:
    604
    Just to make sure, You got muffler packing right? My 07 kx250f did this, I pulled the cap off and dust fell out.
     
  3. pimpit_r6

    pimpit_r6 PR Member

    Location:
    Ellsworth, OH
    Well after a long day of work I wrenched on my bike to see if the packing was toast. I have fresh packing here in my garage and to my surprise the packing was pretty good. No burn holes or brittle fiberglass pieces. Packing was light brown in color. So I resealed the muffler with a hi temp sealent. . I installed the new fuel screw two days ago and come to find out that 2 1/4 turns was way too rich. The motor ran clean and crisp at 1 1/4 turn out. Waiting to test the results this sunday at the track.
     
  4. pimpit_r6

    pimpit_r6 PR Member

    Location:
    Ellsworth, OH
    Everything went well today. Just a few pops coming off 3rd gear pinned. Everything seems ok.
     
  5. SCHAFFERNOCKER

    SCHAFFERNOCKER PR Addict

    Location:
    Canton Ohio
    Racing Number:
    604
    glad to hear you fixed the issue
     
  6. pimpit_r6

    pimpit_r6 PR Member

    Location:
    Ellsworth, OH
    Found out why there are a few pops on deceleration . . .The left side intake valve lash is off by .002 New shims on the way so I can get the valve in spec.
     
  7. TPMX #8

    TPMX #8 PR Addict

    Location:
    Hanoverton,Ohio
    Racing Number:
    8
    I just worked On a 250f like yours and had to go to a 48 pilot jet and out 1 1/2 turns
    Went through exact same problems except timing chain was stretched bad
    Replaced the chain, set all valves
    Checked exhaust,repacked silencer
    Still popped till I stepped up to a 48 pilot
    I should add that the bike had a 40 pilot when i got it
    The 45 i put in first did help alot
     

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