kx250f Jetting help

[phranticness]

OK, I'm lazy, my search bar works fine, but when I use the keyword jetting I get mucho pages of results. I can and will scroll through em, but if someone can hook me up with an appropriate link or thow me some advice it would be cool.

04' KX250f Bog from a low speed to throttle anywhere above 1/2. no bog when I accelerate from low speed to below 2/3 -1/2 throttle. mixture screw seems to have the best throttle response at about 2 1/2 turns out. I've got a boyesen quickshot, and I set the accelerator pump adjustment at 2 turns clockwise from stock for the best response.

NOTE: the bike definatly feels lean just off idle, but everywhere else feels good.

I was thinking of dropping the clip on the needle one notch. I also think the slow circut needs enrichment, do I go down one number on the (pilot?) fuel jet.

thoughts????????? thanks folks :think:

 

[Rich Rohrich]

The pilot jetting on these bikes tends to run on the lean side stock, so starting there is usually helpful. Just off idle the needle is in the straight portion so raising it will have no real effect till the throttle is open further.

 

[phranticness]

thanks Rich...............steve

 

[phranticness]

OK, new question same bike......I've got the bog fixed with the apporpriate pilot jet (among the other changes).

The bike runs great for the first 30 minutes or so of riding. But after a while it cuts out under a heavy load from 1/4 to 3/4 throttle. I know the needle setting shoud resolve this, but why only when the bike is fully warm. is it running leaner (vapor problem) when hot?. This condition is really pronounced when I ride in higher elevations, 4000ft and up. this would lead me to believe that it's too rich on the needle. But I've already gone one knotch leaner than the FMF jet kit needle reccomended position and I'm concerned about running too lean...........

So- hot makes it run leaner (fuel vapor, boil)?
Higher elevations make it more pronounced? higher elevation, less O2 = more fuel?

These two conditions kinna condradict each other..........

any thoughts. point out my stupidity, it's how I learn.


P.S. It was the first real rain of the season in Nor Cal. I had to take off from work early to hit the dirt before dark, it was worth it. :)

 

[phranticness]

Well, I tried one richer on the needle and the problem was just worse. I went back two notches leaner and the problem was solved........the bike runs flawlessly. I really struggled with jetting this sucker, but it was worth the effort.......