450X carb question, need help!

I just got my 450X and seem to have a carburetor problem that I can't fix. It felt lean when I got it, the engine didn't return to idle after opening the throttle, it would idle about twice as fast as it should until I let the clutch out a little and that would drag the engine speed down to idle. If I gave it gas again it would keep the high idle until I let the clutch out. I backed out the fuel screw to 3 turns and the same thing kept happening. I put in the next size pilot and it still does the same thing, fuel screw is out 1.5 turns now. Occasionally if I twist the throttle closed really tight it seems to drop down to idle. I'm lost, any suggestions? :naughty:

Have you tried the idle screw yet?


Yea I tried the idle screw, no help. If I turn the idle down too much it dies when it's no in it's "high idles mode". I'm beginning to think there is something in the low speed circut causing restricted fuel flow, making it appear lean. I talked with the dealer and he is going to pull the carb and clean it, then we go from there. Good thing I have the Honda warranty to fall back on...........

I had to fuss with the idle screw on mine too, around 1/4 to 1/2 turn in made the problem go away and now it's fine.

:naughty: yup mine did that too I just turned the idle screw back till it idled properly but that high idle thing was annoying

turm the air screw all the way in -then back it out 1 3/4 and put a 150 main jet in.thats what I did until my JD kit comes then all problems will be solved. :naughty:

turm the air screw all the way in -then back it out 1 3/4 and put a 150 main jet in.thats what I did until my JD kit comes then all problems will be solved. :naughty:

A 150 main jet sounds a little small. What size is the original main jet? Also, the FCR carb adjustment screw is a fuel screw not an air screw.

142 is stock . fuel /air the one on the bottom of the carb.

It WILL NOT BE FINE!!! not until you buy a new needle from honda,you can turn screws all day but you will have a rich off idle condition and a lean popping on decel,that is if you really pay attention while rolling the throttle on smoothly in any gear but first. of course in the time it took to write this you could know EVERYTHING you need to know about your new bike by going to WWW.MOTORSPORTS-NETWORK.COM and clicking on the 450x in 5 minutes you will learn so much but you probably like all the info just handed to you right, ok, 1 7/8 out on airscrew new needle,3cc's of fork oil in the bleeder caps etc.......... :naughty:

Hummm......sounds like some others are having the same problem. (Sorry Autosprit, you were right, adjusting the idle is the key). Has anyone had this problem and installed a JD jet kit and have it go away?


There is another area of the carb that can be causing this problem: The "Slide Plate".

My CRF450R had the same problem, and it turned out to be the removable plate that is attached to the front of the Slide. It is only held in by friction, and if it falls loose, it will cause "HANGING IDLE". This is a common problem on the '02 CRFR, or if it was assembled wrong at the factory.Remove the slide, and glue the plate in with 3M adhesive, and the problem goes away. This plate is only held in by the friction of a rubber seal, and it pops out easily. You will never need to change the plate, unless you put that carb on another bike (another model) that uses a different Slide Plate tuning.

Also, most of the carbs have assembly grease in them, which clogs up jets, causing weird problems. Rotate the carb, remove each jet, and blow it out. Look into the bowl, and you will also see some crap at the bottom.

Good luck

I am still having this hanging idle problem too. Has anyone figured out what is causing it yet for sure?

Sounds like the same problem I had. It is a lean issue. I bought the JD kit and jetted for the 4000'. You change the main jet to 165, open the side vents and install the red needle with the clip in the 4th from the top position. It is easy! Now I get 4th gear wheelies!!!

Make sure your hot start is full seated as well

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