Sticky throttle after jet change.

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InsaneFurball
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Sticky throttle after jet change.

Post by InsaneFurball »

So i just attempted my first jet change because my bike was bogging heavily in the low end. I changed the low end needle from a 45 to a 38, put the bowl back on, fired it up and now it's still a tad boggy and the throttle seems to be sticking.

The cable isn't kinked or snagged but when i give it a rev the idle will die down and stop at a certain point before dropping all the way back down. I thought the air screw may have been the problem, but i've had it anywhere between 1 and 3 turns out without any change.

One thing i did notice though is after i put it all back together and turned the fuel tap on, the float wasn't stopping the fuel after the bowl was full, so it was flooding like mad... i tapped on the bowl and gave the throttle a few pumps and the flooding seemed to stop.

I really dunno wtf is going on... am i in over my head?

By the way, i dunno what size the main jet is, top end power has never been an issue so i've never pulled it out.
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Julien D
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Post by Julien D »

You've gone too small with the pilot jet. What made you think you needed a 38?

Read this.

http://kdxrider.net/forums/viewtopic.php?t=1156
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InsaneFurball
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Post by InsaneFurball »

Somebody on thumpertalk recommended it to me actually... :neutral:
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Julien D
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Post by Julien D »

making blind jetting recommendations is like playing russian roulette with someone elses bike. Not cool. Luckily you are not likely to damage anything by being a bit too small on the pilot. Your symptoms definitely sound like a lean condition though. What position is your needle in? What's your elevation? Normal riding temps?
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Post by cornishwrecker220 »

is your bike a 200 or 220?..deffo to lean on the pilot..change it to a 42..air screw to 1.5 (as a base setting) needle clip on the 3rd setting check your main jet..142-148 if a 220 & take it from there.
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Post by Mr. Wibbens »

If you messed with the needle at all make sure you got the plastic ring down in it's groove properly
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InsaneFurball
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Post by InsaneFurball »

Argh can't work out how to multiquote here.

Oh well...

The bike is a 250, i didn't touch the needle or slide, so im assuming it's at it's stock position.... whatever that might be.. All i did was loosen the clamps on the airbox boot and front of the carb so i could spin it around to access the bowl.

I checked for the elevation of my home town and all i could find was something that refers to 13metres above sea level... i guess that's what you're after? Riding temps are around 25c/77f max.

I have a thread posted elsewhere aswell and somebody mentioned it could be the emulsion tube that's worn? Which sorta makes sense to me, cause i know these things come rich out of the factory, but with the standard jetting it shouldn't have been as boggy as it was. Plus the fact that leaning the pilot out didn't do much for the bogging issue.
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Julien D
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Post by Julien D »

Ok, anyone know the stock jetting for a 250? 38 would seem WAY too small for the pilot.

For what it's worth, a bike can feel like it's bogging because it's too lean, or because it's too rich. A rich condition will be more like a sputter as it loads up. A lean condition will be a hollow sounding bog. Either will drop power considerably.

Alright then, so lets start at the beginning.

Before you work on the jetting, you need to know that compression is good and there are no leaks in the main seals. Once that is out of the way, you should take a look at that jetting sticky I posted and follow it step by step. Seems like a pain in the ass, but really, it's necessary. We can guess at jets to throw at it all day long and get you nowhere.
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Post by nearma12 »

>|<>QBB<
juliend wrote:Ok, anyone know the stock jetting for a 250? 38 would seem WAY too small for the pilot.
I ran a 38 pilot in my KDX250. The stock jetting is 42/165 if I remember correctly. 45 piot is way too rich. I tried 42, 40, then finally settled on the 38.

Now, jetting is not the only issue with the 250. The slide and needle are a little rich as well. The entire carb needs to be re-worked for that engine to run as well as it was intended.

Furball - If you need any info on the KDX250 carb/engine work, just ask. I went through the entire process with mine.

As far as the problem, you probably need to pull the top of the carb off and check everything.

Make sure:

The top is screwed on properly.
The slide/needle are in good condition.
The spring is installed correctly.
The plastic ring on the spring isn't misaligned.
1991 KDX250
2000 KX250
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