Uncontrollable high idle

[edz250r]

I have a used Keihin 38mm airstryker that I put on my 250R. It starts fine, but it idles real high and doesnt change RPM regardless of how much I screw in/out the black idle screw knob. I think I have a 45 pilot jet in the carb.
Anyone know what could be causing this?

[duke416ex]

Is the needle set right in the carb, have you looked in it to be sure the sliders are working properly?

[edz250r]

I'll recheck, but everything should be set and working properly. It revs and I can ride it, but the idle just cant be knocked down to a lower rpm.

[bloodhound400]

you might want to check the throttle cable make sure it isnt sticking, that happened to me!

[Juggalo]

check and see if you have an airleak somewhere too

[edz250r]

I'll check that too.

Would the engine die if I screwed the idle screw all the way in or would it still idle at a very low rpm under normal circumstances?

[wilkin250r]

Is there any play in the throttle cable?

[edz250r]

There isn't any play in the throttle when you press the thumb. I also screwed the adjuster on the throttle all the way in hoping that there would be less tension on the cable and maybe lessen the idle as well, but that didnt see to do anything.

Is that black idle screw on the carb have some sort of pin or jet in it that regulates the air for the idle? If so, could something in there be broken?

[wilkin250r]

It's possible that there is something broken or wrong with the idle speed, but a little unlikely. Let's eliminate the easy solutions first.

You screwed the throttle adjustment all the way in? Is there any slack or play in the cable at all when it's adjusted fully in?

I'm thinking perhaps the throttle cable is holding the slide partially open. I've done this before on purpose, because my motor wouldn't idle at all, and it kept dying whenever I let off the throttle coming into a corner.

[edz250r]

wilkens...I'll check the play in the cable. I'm not sure if I'll have time to fiddle with it tonight since I already have other plans. I do remember tightening the idle screw all the way in and then all the way out to about the point that the screw was about to come out and no change in idle speed. I'm hoping that its only something like the cable hanging up and holding the slide open at a point higher than the idle screw could compensate for.

What did you do to correct your carb when it would idle at all other than pulling on the cable? My friend has this same problem now!

[wilkin250r]

Originally posted by edz250r
What did you do to correct your carb when it would idle at all other than pulling on the cable? My friend has this same problem now!

The short answer is; I pulled my head out of my a**!

It's a 37mm carb, and it was on the quad when I first bought it. It also idled fine when I first bought it.

I bought a new motor, so I swapped the motor and carb out, but had some problems, so I swapped the old motor and carb back in.

I never changed the settings, but for some reason it didn't want to idle after that, even though it was the exact same settings as before. (compression was good, motor was in good condition). It wouldn't idle at all. The plug was black at idle, so I went down a pilot jet, but the problem was still there. So I went down another, and still another. It STILL didn't idle, and I went down 3 sizes on the pilot! My logic was very simple. If it ran fine before, I shouldn't need to make drastic changes, I shouldn't need to change more than one or two jet sizes. Something else had to be wrong.

Then, I pulled my head out of my a**, and looked in the manual, and asked a few other people what they were running. It turns out I wasn't just rich, I was WAY rich on the pilot. I was running a 158, so going down to a 150 still didn't fix the issue. I went down five jet sizes on the pilot, down to a 145, and now it idles perfect. Now, I'm wondering how in the world did it ever idle before with a 158?!? :huh

So, take my advice on the subject. Just because "it ran just fine before", that doesn't always mean the settings were correct to begin with.