2004 crf 250 jetting
  • Bigbry1979
    Posts: 2
    Joined: Tue Jul 10, 2018 2:20 pm

    2004 crf 250 jetting

    by Bigbry1979 » Mon Aug 13, 2018 9:25 am

    Ok so I've got a crf 250 2004 which had all kinds of problems when I bought it one being the carb so was told it needed to be replaced so only one I could find was one off a rmz 250. Got it fitted and bike fired up and ran ok but after a couple of hour it started misfiring the bike also had a rattle so put it in for a bottom end rebuild also fitted a new spark plug. Went out on Sunday and after a couple of hours bike starts misfiring and shooting flames out of the exhaust. So pulled the carb off to clean it and noticed it's running a 178 main jet and a 68 slow jet also checked the spark plug and it's black. Would you say the jets are causing the plug to foul and causing the misfire? Also when I go down hill with no throttle on it pops and bangs could this also be down to jetting? Bike won't idle either. Sorry for the long post
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    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: 2004 crf 250 jetting

    by JimDirt » Wed Aug 15, 2018 1:43 pm

    Welcome to the site !! \:D/

    Did you post this in the Jetting section of the forum , Leardriver our resident carb guru hangs out there , and could guide you to what you need to do , especially since you're using a carb off another brand , as some parts might be different and contributing to your issues

    Also , what is the specific reason you replaced the carb ?? , was something damaged beyond repair or what was the specific reason you could not use the OEM carb ?? , because unless something was worn out or damaged beyond repair , I would use the stock carb rather than one i know was not made specifically for your bike , they are all similar , but that does not mean they will work without serious tweaking or major work that might not give you the best function compared to the OEM carb being rebuilt

    It would also be very important to list your elevation where you ride , as that has a major factor on what jet size to run

    You need to list:
    Main Jet size
    Pilot Jet size (its the long skinny jet)
    Needle Clip Position (how many notches down from the top the clip is)
    Elevation (the elevation the bike is at and the elevation you usually ride)
    What model carb it is (this will help him determine what he is working with as opposed to the OEM carb) each carb should have a part number on the side right about where the bowl lip is
    2020 CRF450R
    2006 CRF450X
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    Weiser , Idaho

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