Ninja EX250 carb problems

Discussion in 'Motorbike Technical Discussion' started by Anthony, Jul 7, 2007.

  1. Anthony

    Anthony Guest

    New bike that is not under warranty anymore is giving me some annoying
    issues. The Ninja forum is starting to ignore my posts because they
    don't know what is wrong.

    I did a 500 mile post-break-in maintenance on it and adjusted the
    valves. I checked the clearances three times before putting the
    covers back on and everything was correct as it should be.

    My problem is hanging revs and what seems like very lean running. The
    bike ran GREAT when I got it, then it sat for three weeks, I did the
    valves, and now it won't run right which pisses me off because I want
    to RIDE IT!!! Difficult to rev up the engine through a huge flat spot
    and it usually tries to stall. Once it does rev up, when you release
    the throttle, the revs HANG and take about 8-10 seconds to come back
    to idle from about 6-8k RPM.

    The throttle cable is not sticking/binding
    and there are NO vacuum leaks. The boots and carbs are brand new,
    like I said, and very clean. The carbs are not gummed up anywhere and
    the float heights are correct. What would cause it to run so lean or
    to have such horrible response to throttle input?

    I suppose I could have messed up during the valve adjustment, but that
    badly? (done valves on many cars, same idea) and how could a botched
    valve job make my bike run lean (or mimick lean running)

    I think it has something to do with these CV carbs the EX250 uses,
    which, so far, I think are pieces of crap. Everyone says these bikes
    are reliable, well, mine has been trouble since day one and I can't
    even ride it. My wife has Buell that is faultless. WTF! I would
    appreciate any suggestions.
    Anthony, Jul 7, 2007
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  2. Anthony

    Anthony Guest

    Admittedly "pieces of crap" is a bit harsh, but I don't understand why
    they are not working like they should be on a brand new bike. I do
    live over 5,000 feet, but that would cause a rich mixture if anything.
    I have not removed the diaphragm covers, so I didn't pinch a

    Is there a way to test the slide with the carb off the bike? It seems
    like, based on the symptoms, it might not be responding to throttle
    input that way it should.

    With the carbs off, looking in the venturi, what position should the
    slides be in? There is space under mine, but I don't know what is

    I can check the valves agin, but I erred on the side of loose, rather
    than tight when I adjusted them. How about ignition timing?
    Anthony, Jul 7, 2007
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  3. Anthony

    Badger Guest

    Damaged/missing/non-OEM air filter, airbox halves not seating, gummed up
    carbs, choked fuel filter, dislodged vacuum takeoff, sticking cold
    start(OK, that one won't make it run lean) to name but a few. Some of the
    above can make it run rich. At least one of the above can utterly bollocks
    up the mixture in weird ways. Too lean in part of the range, too rich in

    What else did you do?. Tried undoing it?
    If you really made an arse of the job and set the clearances too tight, your
    poor engine could be trying to digest its own exhaust, blowing a
    substantial amount of mixture back in to the carb, but that tends to richen
    it as it passes back and forth across the jets. It can push just enough
    exhaust past the inlet valve on the exhaust stroke to render the initial
    part of the intake useless, as all it gets is exhaust. You really would
    have had to have made a real mess of the job though.
    <thinks very hard ( stop it at the back ) >

    Nope, I have never had any real trouble with CV carbs that I can't put down
    to neglect on my part. In fact, I have never really had any issues with
    carbs unless some butcher with no clue and less finesse has been there

    Pay a shop to sort it out. Bikes are not cars.
    Badger, Jul 7, 2007
  4. Anthony

    Anthony Guest

    Thanks for all the hints and suggestions. I have a few more things to
    look at before paying somebody to do it.
    Anthony, Jul 7, 2007
  5. If you fiddled with the valves, then on a newish bike, I'd suggest you
    fucked something up.
    The Older Gentleman, Jul 7, 2007
  6. Anthony

    paul c Guest

    Do you mean 50% B12 and 50% gas?

    paul c, Jul 8, 2007
  7. Anthony

    paul c Guest

    paul c, Jul 8, 2007
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