04 kx 125 tuning

I have the same bike, and I know exactly what you are talking about...

Change the jetting
here is what I jetted at, but it changes for temps and altitude
Main jet 400 (stock:420)
Pilot jet 35 (stock:40)
Stock needle, in the stock position
Im not sure what about my airscrew is at now,

And by going up to 40:1 with oil you are actually richening you mixture, If I were you I would stick with a good 32:1 ratio, You gain absoulutly nothing running 40:1

More gas makes it richer, I ran almost those same jetting spec's he suggest yes they work awesome but I ran the needle clip position at #2 from the top and the air screw was at 1.5 turns out and I ran it at a 40:1 ratio.

greenman06 said:

I ve been using Bel ray h1r, what is a better mixture to run with since its a semi sythetic? Do u guys think by just changing the pilot to a #35 that would help, since its loading up when off the throttle or low throttle? Do you guys think the powervalve would be an issue or the float height?sorry for all the questions......

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Powervalve wont effect jetting, unless it is extremely gummed up, I would just leave it alone until you rebuild your top end...
I dought that the float is messing with it... If it never bogs after you have been on the gas for a long time, or doesent leak gas from the overflow your float is most likely fine... But be warned, the float on that bike is extremely picky... at least mine is

If I were you, for a start I would go to a 410 for main, 37.5 for pilot, and play around with the needle and air screw, and go from there.

Running too rich is alot better than running too lean... Believe me on this :)

If I were you, I would goto a 32:1 oil mix ratio, I personally dont see why anyone will goto 40:1 or even less oil... Because these bikes need the absolute most lube they can get.
The only thing that I see better about mixing Less oil is, less cost.
I mix mine at 28:1 with maxima formula k-2... Works great, and I never have any problem with it loading up, I can put around all day, and then get on the gas... It will smoke like a bi*ch, but wont cough or hesitate at all :laugh:

greenman06 said:

thanks sir, i went to get different jets at my local dealer and there are clueless what it takes, talking about different sizes and shapes but couldnt pinpoint what i should get. They were talking about hex shape and big hole small hole. Are the carbs all the same on the 04?michuni right? Do u have part numbers for those #410 and #37.5?

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hahah wow, you got a nice damn dealer there... :bang: :bang: :bang:

I dont have the part numbers, so I cant help you there...

But just say for examle "i need a size 400 main jet for mikuni TMX-38 carb, Or say what kind of bike you have... they should have that on file.

Good luck