YZ 250 carburation
  • CRman2002CRman2002
    Posts: 63
    My '03 smokes quite a bit until I run it hard, then it doesnt smoke as much. Lots of spooge too, and I can turn the idle screw all the way in and it will only make the bike go just a little bit over normal idle speed. Everything is stock and the carburetor has never been fooled with jetting wise, and compression is very good. any tips on how I can fix this?
  • BleedMarshallBleedMarshall
    Posts: 2,572

    What jetting do you have in it now? I assume you have owned the bike since it was new?

    By saying "everything is stock", I assume you are talking about the bike and not just the carb, yes?

    What are you running on your mix ratio, and has there been aby severe weather changes or altitude changes such as a move from one state to the next?

    When was the last time you checked your exhaust system and repacked your silencer?

    You could have a clogged jet, or a bad jet in it causing an issue, or even all the way to bad packing as I have seen it cause a few issues. If the issue just started, it could be due to colder weather or you may have another issue such as old gas/oil mix, or even a dirty filter causing the bike to run rich as it is restricting air. If you have recently changed exhaust systems it can cause lean to rich issues depending on what you changed as well, but if not...*shrugs*.

    Check your air filter and make sure it is clean, and make sure your carb is set to normal/factory specs before you go any further. Also make sure you have fresh fuel ad oil, and make sure the silencer does need repacked. Carbs can be a pain even if you know what you are doing. I had an issue with my '06 YZ125 that drove me nuts for awhile, and I finally got it sorted, but it still ticked me off. Hahaha!

     

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    2006 YZ125
    2006 300 XC-W
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  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    I love cheddar poppers!
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • Kiwi450xKiwi450x
    Posts: 3,635
    How's your YZ 250 Maple?
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    If you can't fix it with vicegrips and/or a sledge hammer, it ain't worth fixing...
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  • Kiwi450xKiwi450x
    Posts: 3,635
    Surely you could be more helpful than that.
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    If you can't fix it with vicegrips and/or a sledge hammer, it ain't worth fixing...
    image
  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    O yeah sorry. I went one richer on the pilot jet but started fouling plugs so put in the stock pilot for next tear. Stock mains fine and i went back to stock n3ew needle 2nd clip from the top. My plug fouling got bad. One day i went through 3 plugs. Stock pilot should fix that.
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    What jets r in ur carb now?
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • CRman2002CRman2002
    Posts: 63
    to BleedMarshall:

    I'm the 2nd owner, 1st owner hardly rode it and left EVERYTHING stock, even the jets. He has been living in the same area as I am for a few years now. I've recently repacked my silencer and run a 40:1 mixture with motul oil. air filter looks new, and when I took the carb apart everything looked very clean. air screw is at factory setting, same with the jets and needles
  • PaulB14PaulB14
    Posts: 8,012
    I would start by dropping the needle 1 or more settings.   Remember to drop the needle you need to RAISE the clip.   This is usually the easiest (not to mention cheapest) adjustment that you can do to your carburetor to clean up a rich condition on the bottom end.  The 2nd option is to try smaller main jets, 1 size at a time only, and keep checking to make sure you are not going too lean on the top end.   These are the places I typically start messing with the carburetor.   I rarely have to change a pilot jet.   Another rare problem is a float that is sticking or set too low, which will cause a rich condition and fouled plugs.  You can check the float for any obvious damage (a hole in it for instance) and make sure it is operating smoothly.  

    Even more rare (this has happened to me only once in 40 years) is a damaged needle (I had one that was nicked and so it didn't seal properly).  You can examine the needle when you take it out to lower.  
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    NW Montana - Where the pavement ends and the fun begins
    image

    2005 KTM 300exc
    1977 SUZUKI PE250
  • CRman2002CRman2002
    Posts: 63
    thanks Paul, the float looked new, same with the needle. Ill try this out and see what I get. You think this could also be the reason why I have the idle screw all the way in?
  • PaulB14PaulB14
    Posts: 8,012
     let us know what you notice when you drop the needle.   You should put the air screw back to the stock setting when trying to dial in the jetting.
    ///////////////////
    NW Montana - Where the pavement ends and the fun begins
    image

    2005 KTM 300exc
    1977 SUZUKI PE250
  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    I agree on the needle adj paul. Id also like to throw in a question. Did the bike start without the choke pulled?
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • CRman2002CRman2002
    Posts: 63
    to Maple Leaf MX:

    ya know, I havnt even tried that yet, but I wouldnt doubt if it could. Ill get back to yall later today or tomorrow after I try these
  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    Ok
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • CRman2002CRman2002
    Posts: 63
    dropped the needle, it is now at the lowest setting (clip in the top position) and the bike does not smoke as much, havnt noticed any spooge yet. air screw is at factory setting 1 complete turn out. It is more crisp, responsive, and powerful now. but the idle screw is still turned almost all the way in just to keep it idling
  • Maple Leaf MXMaple Leaf MX
    Posts: 12,823
    Be careful with ur needle. What does ur plug look like now?
    Expect to die whenever but dream to live forever

    ..the good times on the old DR board will never be back! RIP!
  • PaulB14PaulB14
    Posts: 8,012
    I would turn you air screw out a full turn from where it is now.   This should bring help out with the idle
    ///////////////////
    NW Montana - Where the pavement ends and the fun begins
    image

    2005 KTM 300exc
    1977 SUZUKI PE250
  • CRman2002CRman2002
    Posts: 63
    I haven't checked the spark plug yet, I ran out of time that day and havnt gotten around to it since. I can try the 1 extra turn out with the air screw, but the bike seems to run near perfect where it's at right now
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