KX 250 High Idle, Exhaust Leak - Help!

9 replies to this topic
  • ss600

Posted April 27, 2011 - 05:00 PM


SO, I got my bike back together again, engine has 10hrs on top and bottom end, just bought the bike and tore it apart for cleaning etc. Took the carb apart, drained fuel, new coolant, tightened/checked bolts, new tires etc. After cleaning the carb i put it all back together today with some fuel at 40:1 mix. The bike started on the choke right away, but the idle would not die down after and it idled extremely high. I rode it for a minute then shut it down. Everytime I start it back up, it idles waay too high. Along with this, there is oil spitting out of the silencer and the exhaust port. Will a leak at the exhaust cause an air leak? But, shouldn't the bike lean out a bunch, not run really rich like it is, spitting oil everywhere. Please help! I need some ideas on what to check first.
Oh, the bike is a 98 KX250 running on 93 octane, stock jetting, and a full procircuit system.


  • moose_338

Posted April 27, 2011 - 05:18 PM


Cheak to see if one of the airboots is lose/misallingned
Did you reajust your air and idle screw after geting everything back together?

If that dosen't work i would say you put something back together wrong in the carb.....

  • matt 2778

Posted April 27, 2011 - 05:36 PM


Aside from a full leak down test you can do a quick check with a can of starter fluid. Start the bike and spray the fluid in the vaccinity of the carburetor. If the idle changes you've found a leak. This works for the base gasket too.

  • JTLS

Posted April 27, 2011 - 05:55 PM


Your throttle cable too tight?

  • JTLS

Posted April 27, 2011 - 05:57 PM


how did it run before you took it apart?

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  • ss600

Posted April 27, 2011 - 06:42 PM


If it helps, before I took it apart it was not idling, presumably because of the clogged pilot jet i found. It would start and run, but would stumble and die after. But what about the extra oil coming out? I will definitely get some starter fluid and try a quick check. Any other ideas?

  • taylord_99

Posted April 28, 2011 - 07:53 AM


extra oil is just excess oil. not really anything bad. rather be spitting out extra oil then none!

  • kawizuki

Posted April 28, 2011 - 11:23 AM


agreed ^^^

and after you put the carb together did you move your idle screw back???

  • iggle

Posted April 30, 2011 - 05:16 PM


I've got a very similar problem. took my carb off my 01 125 today, cleaned it and all. done it a bunch of times. Put it back together, positive nothing the wrong way heh(dont see how that woudl even be possible), put it back in and now it start without the choke (and not even a shot of gas?! ***) and then idles to the moon and back. I've checked my air mixture screw, even took my idle screw out some from what it used to always be at. Nothing seemed to help. Any ideas? Supposed to go ride tomorrow, but worried about using it with it idling so high!

  • JTLS

Posted May 01, 2011 - 06:08 AM


I'm gonna say it again... is the throttle cable too tight? It's the most common problem I see when people "clean" thier own carbs.

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