KX 250 High Idle, Exhaust Leak - Help!

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.


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.....

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.

Your throttle cable too tight?

how did it run before you took it apart?

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?

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

agreed ^^^

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

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!

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now