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03 KX144 Jetting Suggestions

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Hello, I have a 03 KX144 from Forward Motion ported for bottom and mid. The bike runs okay right now with 420 main, 40 pilot, and 82 needle in the third position from the bottom (not sure if you normally count from top or bottom). I'm pretty new to jetting.

I use the bike from 3000-6000 ft in Socal. It also has stock pipe with Pro Circuit spark arrestor silencer. Right now I'm experiencing major spooge. It has not fouled a plug yet, but i imagine it isn't too far from it. I included a pic of the plug if it helps. That picture is after riding in Dove Springs probably 3000ft and up to the cabin probably around 6000ft. So, how do I stop the spooge and make the bike more leaner and more crisp?

P1010181.jpg

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Its rich but looking at the pic its not to far off , have you done a flat out plug chop ? some big bore motors need leaning throughout the whole range as they tend to pull more fuel / air due to becoming a bigger pump but still sucking through the same hole (carb) to put it in simple terms

Start with the main and pilot then move to the needle you may need a leaner item if lowering it doesnt cure your woes

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I just read this link... http://justkdx.dirtrider.net/printcarbtuning.html Long read but I learned a lot. I think I can handle it on my own now with their guide. I have not done a plug chop yet but the next time we go out to ride I will. How much leaner do you think I should buy the jets? Maybe buy 400, 410, 35, and 37.5?

Elevation isn't going to affect the jetting as much as temperature. Temps affect on jetting is many times greater, so what you should be thinking about is temp at the bottom vs temp at the top of your run. best just to go by every 15 degrees of temp change you need to go up or down 1 pilot and main size. and as it gets colder air becomes more dense, so you will need bigger jets, opposite for hotter.

getting it correct is the difficult part, once its there its no problem getting the correct jets to jet for any riding conditions

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my guess is that your kx has a mikuni carb check the float level in the carb because a high float level tends to spooge in that carb. when i had a 144 rm the float level was too high and it spooged like hell.

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The link to the article you posted is a good one and if you follow it you will be way ahead of most of your fellow riders when it comes to jetting. I would like to add some insight to your original question. It looked to me like your main issue is the spooge and second a minor lazy rev. If you think about where you normally ride and at what throttle angle you may be able to kill two birds with one stone. The engine is obviously running fat by the picture and most likely you are in the 1/4 to 3/4 throttle angle the majority of the time that is where I believe you should focus your tune. It just so has it that the manufacture gives us a variety of options in the needle as far as clip position. I have only ridden at that altitude once and at that time I was not in control of my jetting so I can't offer any first had advice but if it were me I would start by just moving the clip on the needle one step leaner (move the clip toward the top) and test ride for seat of the pants feel and sound. Then go one more step leaner and retest. My guess is you will be happy with the results because the needle jet and jet needle cover the most broad range of throttle angle you will notice the biggest difference there. Being fat on the main is not a bad thing. This insures plenty of lube when the engine needs it the most.

Now I'm not telling you to not do it properly and by the book... just another way to look at it and solve your problem possibly with less headache.

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I'm gonna bring this thread back from the dead. The KX144 is running well and the wife loves it. I ended up with a 35 pilot, 82 needle in top position, and a 400 main. The throttle response is better but I'm still getting some spooge that is annoying to clean up every week. I'm gonna try a leaner needle. After some searching without finding anything, I'm just gonna ask a stupid question. Would in my case a 83 needle be leaner or a 81? I'm not sure if the needle goes by length or just like the other jets the bigger the number, the more fuel it delivers.

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Bump for a quick easy answer so I can order parts. Which is leaner 81 or 83 needle jet? I'm on the top clip of my 82. I think I need to go a good bit leaner. How many jets leaner should I buy?

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