07 CRF250x idle issue and low end bog
  • czyfbm
    Posts: 3
    Joined: Sat Apr 17, 2021 6:55 am

    07 CRF250x idle issue and low end bog

    by czyfbm » Sat Apr 17, 2021 7:33 am

    2007 CRF250X with air box open, FMF Q4 exhaust, standard header, JD Jetting, and smog delete.

    Rebuilt with OEM Piston, rings, valves Intake/Exhaust, valve stem seals, new spark Plug, adjustable fuel screw:

    My old starting procedure was to hold kill switch and kick bike 3-4 times then full throttle 3 times to squirt fuel in cylinder.
    Bike would start cold with choke and one kick.

    Now when i do the same procedure the bike doesn't start for several kicks and i have to hit the start button to get it to fire.
    Once running on choke the bike is idling high and sounds like it is missing on and off.
    turn choke off and the bike will idle but also sounds like it is smooth and then has a slight miss, then back to smooth, then slight miss and continues to repeat.

    Also the bike has a slight low end hesitation/bog when going slow and opening the throttle to full.

    I have taken the carb off for cleaning and inspection and was clean but took apart anyway and checked jets and passages. also disassembled accelerator pump and checked diaphragm and passages. All were clear and clean.

    Screwed air screw in all the way after the bike was hot and the bike didn't stall. Could the rebuild have changed the jetting required to run correct again? I have the suggested JD jets, needle and clip location, and fuel screw turns out.

    I will check the accelerator pump timing next but I am looking for additional suggestions to the weird idle and bog.

    Bike ran great after the rebuild, very strong and same as when it was new. Perfect idle and no low end bog.

    After setting the winter now is running weird. No signs of bad fuel and residue due to ethanol gas.

    What am i missing at this point???

    Concerned with the none smooth idle that almost sounds like a slight miss (Maybe running to rich??).
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: 07 CRF250x idle issue and low end bog

    by JimDirt » Sat Apr 17, 2021 10:08 pm

    Welcome to the site !! \:D/

    The fuel screw is concerning , that means that something is not sealing .....it should want to die when you get anywhere below 1 turn out ... You mentioned "no signs of bad fuel" after sitting all winter .... that is concerning , how did you determine the fuel was good ?? , and if it was Ethanol gas , then most likely it is bad , it will work fine in your car or lawn mower , but not in these bikes after sitting that long (anything longer than 2 months is a crapshoot on Ethanol gas)...... in the "rebuild" of the carb , did you replace the O-Ring that goes to the fuel screw ?? , and if so , did you make certain that you got the old one out ??? , that could be the issue with the bike running with the screw in all the way ....

    In the rebuild of the carb , did you replace the Needle Jet ??(this is the long brass tube the the Main Jet goes into that sticks up in the venturi and the Needle goes into) , if it is worn you will get a a erratic idle , or a rich/lean condition mainly noticeable at idle

    I would also be concerned wit h a internal passage blocked in the carb ..... and yes the A/P can be out of time , you can confirm that by filling the bowl , then twisting the throttle and watching the squirt from the rear of the carb , it is best to do this with the subframe raised so you can see directly into the rear of the carb and see the squirt , or you can do it with the carb removed and fill the bowl by holding the carb next to the fuel valve and opening it up with the line connected , then remove it and work the throttle till it squirts , it needs to just barely miss the slide or the timing is off especially if it hits the slide

    So I would look for a vacuum leak , a fuel leak from possibly the needle/seat not sealing and gas raising into the venturi and getting sucked into the engine at idle causing the irregular idle by richening the circuit

    Also look at the O-Ring on the slide plate , if it is bad it will not seal with the vacuum of the engine and cause issues ....
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • czyfbm
    Posts: 3
    Joined: Sat Apr 17, 2021 6:55 am

    Re: 07 CRF250x idle issue and low end bog

    by czyfbm » Sun Apr 18, 2021 8:27 pm

    Thank you for the reply and information for trouble shooting.
    I took the carb off and cleaned it again and found that the pilot circuit was partially plugged. Sprayed carb cleaner through and it opened up.
    The bike is now back to starting perfect and I will take it out for a ride Monday to test how it runs hot and if it still bogs slightly at low end.
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: 07 CRF250x idle issue and low end bog

    by JimDirt » Sun Apr 18, 2021 11:12 pm

    Keep us posted on the results ... 8-[
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • czyfbm
    Posts: 3
    Joined: Sat Apr 17, 2021 6:55 am

    Re: 07 CRF250x idle issue and low end bog

    by czyfbm » Mon Apr 19, 2021 7:52 pm

    JD jetting suggest 65 main and 42 pilot.
    I had a 45 pilot in the bike so I changed it back to the 42 stock pilot.
    Still had a slight low end bog until I turned the fuel screw out 3 turns.
    The bike now rips out of corners with no hesitation and a wheelie monster.
    Weather here when tested was 42 degrees.
    Stock fuel screw is 2.5 turns out so I’m in the ball park due to the cold weather.
    I will have to recheck the fuel screw when the weather warms up to make sure the response stays the same.
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: 07 CRF250x idle issue and low end bog

    by JimDirt » Mon Apr 19, 2021 9:59 pm

    Turning the fuel screw OUT means it wants to be richer , so did you try the #45 ?? , I would and try to get back a bit on the fuel screw closer to 2-2-1/2 , try the #45 and see what it does ....... OR , Lower the Needle clip position by 1 notch and see if that brings your screw back in away from 3 a bit ...
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Aussiecrf230
    Posts: 1962
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: 07 CRF250x idle issue and low end bog

    by Aussiecrf230 » Tue Apr 20, 2021 2:09 pm

    At 3 turns out vibration can unwind it the rest of the way.
    Nothing good ever comes of anything falling of a bike.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas

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