I think I need a different needle in my 250r. I have a stock carb with fmf rev pipe k&n and other stuff.
Anyway i had a shop dyno and tune it for sea level. I'm running a 52 slow jet 150 main and a DEJ needle and change between the 3rd and 2nd leanest most of the time. And it runs fairly well.

Now when I go up into the mountains 4500 -6000ft, I went to a 145 main, idle screw out about 2 turns and needle clip in the leanest setting.The top end seems fine but i get a lot of sputtering 1/4 to 3/4 trottle. And possibly a little rich at 1/8 to 1/4 In the mountains its all trail riding I would like to run in the mid trottle more than all out. But as it runs now I have to clean it out every now and then. Plus the fuel mileage is not the greatest while running like that.
So I think I need a leaner needle but I'm not sure how much jump I need. I've been looking on some sights at charts for keihin needle selections. I'm thinking like a CEJ would be the next step leaner. Its pretty much the lenth of the needle I'm looking for, right? I might perchase others around the size i need with maybe a slight lean in the off idle too, like a DEK,DEL, CEK or CEL

Maybe I'm just trying to get around changing the slow jet.

If someone is knowledgeable about this stuff please let me know,
thank you.

 

Try a 48 slow jet and a 155 main needle 2 notches down.