Put 120 miles on my 09 klx250s the other day, got gas on the way home, it died 5 miles or so down the road... I'm a reader so this is what I've done. Changed the gas, as its ran fine till I got gas, changed the plug, pulled the carb and cleaned it... found nothing at any point.
symptoms: Runs fine with choke on, as long as the choke is on, runs normal. Acts like its running out of gas. Will run above 5000 rpm, not below with choke off. Runs almost normal for a couple minutes... then sputters. Even this way, it will act like its out of gas in about 3-4 min. I've taken the carb apart 3 times, I find nothing. The carb is spotless, all jets clean and spotless. What in the world am I missing?
Now before I open the carbs, it was doing opposite of what its doing now. It would ONLY run with choke. If you have it gas it would die, like kill switch die. Now its acting like its out of gas, but seems to have it. The petcock IS working. drains very fast.
Pulling this carb off and on is killing me, nerves are shot! I've read and read all over the net and here, I've cleaned it, I've done everything I know to do... I welcome new ideas... before I bury it in the yard!

 

Well, it sounds like a classic plugged pilot jet from those symptoms. This usually occurs from sitting idle for a long period...not from getting gas. Still, you can get it to run at low rpms with the choke, and you can get it to run when the rpms are up in the needle and main jet ranges. Sounds like the pilot/idle circuit is plugged.

 

Kinda what I thought.. took it apart again, STILL acting the same. If I didn't know better id say the plunger for the needle is getting stuck... how would I confirm it actually working? The bike hasn't set long. I ride it pretty often. I did a great day on it that day, getting gas twice before, no issues. Then BAM! Riding the next 7 miles on choke at 25 mph... beats walking I guess. Think I should order all new jets? Is this a good time to rejet it? If so.. what is good for all stock bike? Stock?
And thank you for the reply. I really am pulling my hair out. Bald by Sunday at this rate!

 

Oh... what gets me is it will run fine for 3-5 minutes, then do this. After said 3-5 minutes, it acts like it is out of gas. I confirm the float working, confirmed the thing can actually get as much gas as it wants...

 

Something blocking/pinching the fuel tank vent hose?

 

Drop the carb in from the top sideways. Turn the carb (like how it's normally positioned)into the air boot collapsing the air boot like an accordion. That will give you enough room to put the front of the carb into the other rubber intake on the cylinder. Spray wd40 on both interior rubber clamping surfaces to ease installation. I've done it so many times dialing in the fcr35 it's a 10 minute job.

Pilot jet carb tract is so miniscule, you really have to watch for carb cleaner to spray thru the tiny hole into the carb throat.

 

Side stand switch?

 

maybe a piece of crud got in the carb... the "only runs with choke on" usually means something is blocked

submerse the carb in carbcleaner?

 

I totally here you guys with something being stopped up, I can see through the jets, spraying them gets spray shooting out. I remove it! Same thing. I'm 100% going to have to set it down for a bit. I'm aggravated. I hate it when I can't figure something out.

 

Seriously, check the side stand switch. It may be only partially connecting. It might not be the entire problem but maybe magnifying it.