I need to Rejet the kx and need some tips, are there any Carburetor engineers out there? lol
Its got a full FMF System, Fatty/shorty
Stock engine
thats it.
Any help will be appreciated.

fuel octane + oil mix ratio / elevation + temp - rpm range = jet size/rider age

crap, forgot to factor spooge, spark plug,and moon phase.

see it's easy.

why rejet? is it presently lean or rich, and at what throttle opening? kx isnt enough to work with. what model kx etc.

moon phase..... lol very true!!

throw chicken bones at it, and fill the rad with holy water. works on ktms.

2005 kx 250 2 stroke, hahahaha Tobes that really funny! lol
Well if i put a new exhaust system on, then that means its lean and at quarter to 3/4 throttle.
Another thing im doing is dissembling the ting to clean the stupid power valve that jm didnt clean but we told them to clean. theres a huge build up of unburned premix. Thanks jm. now i have to do the whole rebuild over.

I agree with Nates question. "Why rejet?"

What is the problem? spooge? bog? white plug?

If it ain't broke......

Loss of power, just doesnt have the snap that it should. I cant really explain it, but if you were to ride it, you would notice it easily.

If your "power valve" is gummed up (clean the stupid power valve that jm didnt clean-theres a huge build up of unburned premix), that will most definitely effect your power. Had one in my KTM 300 stick and it was giving me great bottom end, but it had no hit.

It may be something that a good cleaning can fix. Start with that and see if it helps.

-Lee

Yea the stupid thing was leaking when we got it (meaning it was cloged) and we rebuilt it, thinking jm clean the thing we told the to clean. Now we have to do it again.

first we get suckered into a "break in procedure" discussion and that must have gone well enough to bring us into jetting. whats next, politics and religion.

Lets assume it had perfect jetting to start (big ass-umption), and now you have some sort of exhaust that is flowing better and you think its more lean. I would go up 2 or 4 on the main (like 164/165 instead of 160 etc), and raise the needle (drop clip) 1 spot. Go safe and fat, then lean down from there as needed based on the spoog/plug readings. and feel. Just a pipe change should be hardly any jetting change, unless the mix was way off to start. On my ktm oil burners, its surprising how much leaner lots of folks run them compared to the manuals jetting chart. I do need to compensate when running highly oxygenated fuels like the sunoco 104 or vp u4.

I like the ideas of cleaning the carb and powervalve first, and starting with brand new fuel, mixed with either motul or belray HR1 oil first. Start with the basics before chasing the jetting. maybe check for air leaks too at the carb boots before changing brass...

A lot of the carb gurus now recommend replacing the jets every year or two with the current pump fuels. The pilot jets being the most problematic with it's small openings. It only takes one tiny deposit to effect its performance and the costs are minimal to replace.

Also on smokers don't overlook the silencer/spark arrestor...one friend who shall remain nameless went through several hundred dollars of engine work only to find out it was a restricted screen type spark arrestor! Doh!

Cheers