KDXRIDER.NET

Hi every body my kdx has always run a little weird but the thought I best leave it alone and ride as it is than break it and not ride at all but lately its been getting worse and worse has way less power than it used to (will not wheelie in first gear no matter what i do) and now it won't rev out I recorded the sound of me accelerating posted it on YouTube for easy viewing here is the link would be nice if some one could tell me what's wrong.

clean up carb, jet it properly, clean air filter and exhaust.
report what jets you started with

The usual should apply here...
Make sure your intake and exhaust tracts are mechanically sound (no holes in boots, reeds good, KIPS operating silencer freshly packed, new plug, clean filter, compression good, etc). Thoroughly clean your carb. Don't just spray it out, disassemble it and clean it well. Make sure your fuel delivery is good (check petcock, filter, tank and clean). Then run through the jetting guide and ride your new, buttery smooth green monster.

OK so I was not able to buy stuff but I had some free time so I put on my big boy pants and practiced taking of and taking apart the carburetor for the first time (my hands were shaking really bad lol). Anyway so what I found was that the carb was spotless and that the jets had numbers on them the bigger one said 158 and the smaller one said 48 also I googled how to set float height and found out that mine were set wrong so I fixed that also the smaller jet was clogged I blew through it and I was then able to see through it. To check if the petcock was fine I took of the fuel line and turned it to on fuel gushed out really fast so think that's not the problem and from what I read on the internet dirt bikes don't have fuel filters unless u put on an after market one which I don't have. After that I started it, it idled and ran like it used to just fine but the problem at high rpm stayed. Oh well the point of this is to tell you guys the size of the jets, the fact that the fuel flows well to the carb, and that the carb is clean and both needles are in perfect condition. Hopefully tomorrow I will buy carb cleaner, thoroughly clean the carb, buy new air filter, new plug, and new muffler packing, replace all those things and play with the air screw. Oh and the exahst does leak, at the part where it connects ( one part of goes into another under the air box )

You are making progress.
If you have the original silencer you cannot replace the packing. They do clog up and there is not much you can do about it.

Where you are describing an exhaust leak there should be a rubber piece that covers the joint between the pipes. A couple of zip-ties in the grooves of that rubber piece will take care of that leak

The engine sounds very good up to a certain rpm at a maintained speed. Definitely fuel starvation. MAYBE electrical. Either your main jet is clogged or your floats are still too low ...

158 is very rich(your bike is an 89/90) so you should be getting lots of fuel. Did you clean the tiny pin hole directly above the main jet? A electric guitar B string or acoustic lower E work very well.

Float height should be measured 16mm with the carb resting upside down and from the surface where the bowl contacts and the top of the float

Also, your kdx does have a fuel filter, it is located on the other side(inside the tank) of the petcock

check compression and that the reeds are sealing well

OK so I cleaned the carb, replaced muffler packing, and set the floats even higher and put in a new plug decided to ride it first the idle was to low I guess raising the floats makes it lower I had to screw the idle almost all the way in for it not to die. Then I got on slowly rode to one end of block turned around and hit the gas like I usually do except that this time I almost flipped over then I calmly rode back to my house looking like this after my legs stopped shaking I rode it again and it does wheelies not at full throttle in 3 gear so yah bufftester was right about the intake exhaust thing, thank you for nearly killing me

"I had to screw the idle almost all the way in for it not to die"

your pilot jet is most likely off...
follow the jetting guide

x2 jetting guide don't miss steps.

BTW we can only help ya on the bike