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I've got a '93 XR250L that has an idling issue. The carburetor is jetted for perfect response, but the idle is rough and it will die after 10 seconds or so. What I have discovered is that when I turn the gas off, it speeds up and smoothes out. I figure the float needle is not sealing off good when closed, even though I'm not seeing gas running out the overflow. The float looks ok. It's all plastic and non adjustable. I have shimmed it with aluminum foil to close off the gas at a lower level in the bowl, but still have the same problem. I have ordered a new float needle. The idle air screw doesn't make much difference, no matter where it's set. I have pulled the limiter off. Is there anything else it could be if the float needle doesn't fix it?

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The stock float does have an adjustment tab for setting float height.

If yours does not have one, you have the wrong carb on the bike.

https://www.ebay.com/i/201970532206?chn=ps&dispItem=1

On a carb nearly 30 years old, you could have dozens of issues. 

Until you replace the emulsion tube, set the float to factory specs, and check for partially corroded passages, it's hard to say what else might be wrong.

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 The bike is all original, I bought it many years ago with 750 miles on it. Carb is stock pumper carb from the factory with an all plastic float. The only thing metal on it is the pivot pin. No adjustment. Have had it apart many times through the years. The float you were showing is for the XR250R; mine is the XR250L as I stated. I should be getting the float needle in soon and will report if that fixes the bowl overfilling. After thinking about it, can't really see it being anything else. If something was plugged, it would normally be lean, instead of rich at idle.

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Put new float needle in and now have smooth idle. Fixing this made a slight bog just barely above idle show up while riding, but not noticeable unless moving. Taking off, slight bog at about 1/16 throttle and then smooth acceleration after that. The air screw made very little difference. It felt like a slight richness was causing this. I remembered shimming the accelerator pump rod after reading an article online, that makes it squirt as soon as the throttle is turned. I removed the shim I had installed and the bog went away. It was just getting a little too much gas as soon as the throttle was turned. Running perfect now.

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