2003 yz250f wont run with out choke

oaktree25
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oaktree25
My 03 yz250f starts hard even with the choke on. It will take me anywhere from 20 to 30 kicks to fire it up. Once it's running, I cant turn the choke off and I cant give it any kind of throttle. Once it runs for about 5 mins it will allow me to give it throttle and turn the choke off, however, when the rpms drop it just dies. I've taken the carb off and only cleaned the float bowl and the few jets I could get to. Please help me with this!!! 🥺
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kb228
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kb228 8/17/2019 5:13am
8/17/2019 5:13am
Go ahead and put NEW jets in. Theyre cheap. Dont waste time trying to clean them. Soak the carb in cleaner overnight. Make sure your accelerator pump is timed correctly.
Paw Paw 271
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Paw Paw 271 8/17/2019 5:16am
8/17/2019 5:16am
Pilot jet is clogged for sure and maybe the starter jet as well.
You also need to check the valves.

Paw Paw
Racingdanger
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Racingdanger 8/17/2019 5:58am
8/17/2019 5:58am Edited Date/Time 8/17/2019 5:59am
Yes definitely a full carb clean from jets all the way to through ports , soo the whole thing in carb clean then blow out with a air hose , take all the jets out and rememberer they were set at , it will possibly be the valves , it should not take forever to kick and how it dies when the gas it let up and you need the choke , I just don’t the valves and a new carb on my 06 and that was the issue , carb clean and a valve adjustment. Valve adjustment every 15 hrs 20 hrs on the 250’s depends on how much you ride though , I’m ocd so I check em all the time
oaktree25
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oaktree25 8/17/2019 1:01pm
8/17/2019 1:01pm
Thanks guys, paw paw, why should I check the valves?

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suspensionguy
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suspensionguy 8/17/2019 2:03pm
8/17/2019 2:03pm
Only running with the choke is almost always a plugged pilot jet.

They are suggesting to check the valves because hard starting on a four stroke, especially a older one like yours is normally due to tight valve clearance. You should be checking them every 20-30hrs. It sounds fairly neglected, I’d toss a piston in while you’re working on it.
oaktree25
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oaktree25 8/17/2019 2:29pm
8/17/2019 2:29pm
See, I just bought this bike about 2 weeks ago. I've rode it maybe twice. But my buddy took it out and ran it out of gas, now it does this. The guy I bought it from said he took good care of it, but it's hard to believe with the few issues I have seen myself.
kb228
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kb228 8/17/2019 4:47pm
8/17/2019 4:47pm
Youve gotten good direction from everyone. Do all that stuff and i think youll be good to go
oaktree25
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oaktree25 8/18/2019 2:14pm
8/18/2019 2:14pm
So look, I tore the carb all apart, I have everything for it, but while I was looking at it I realized that there is no fuel adjustment screw at all. Could that of been causing the problems?
Racingdanger
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Racingdanger 8/18/2019 2:16pm
8/18/2019 2:16pm Edited Date/Time 8/18/2019 2:19pm
Yes , it may have fell out if you ever road it then started to act like this , they do fall out but it is rare , if you put the fuel/mixture screw back in and it still does the same thing , I’d lean more towards valves , Make sure you turn that screw though a few turns, when it is in the right spot the bike should idle and run fine , you have to do when it is running unless you know where it normally is set , but if that isn’t work , valves
Paw Paw 271
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Paw Paw 271 8/18/2019 3:00pm
8/18/2019 3:00pm
You will need the screw, washer and oring for it. You initial setting should be a bout 2 turns out from seated. With out the fuel screw you will be running rich at low RPMs and lean at any RPM above idle. Are you 100% sure the screw is missing or is it the OEM unit that is very recessed in the carb body?

Paw Paw
oaktree25
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oaktree25 8/18/2019 3:14pm
8/18/2019 3:14pm
I've checked everywhere and there is no screw anywhere. I made sure that I didnt drop it when I took the carb off itself and it's no where. I have one ordered, I figure I will just go through and do everything everyone has said, and I'll put the new screw in and figure it all out. I was just seeing if that could be a big reason to why it's running like it is.

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