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jetting bog on crf250x

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I have a bog on my crf 250 when the throttle is cracked open suddenly. I have installed a 42 slow jet, raised needle three notches, and installed everything from a 130, 140 150 and a 160 main, with no change

Today, I just turned my airscrew all of the way in, and the bog pretty much went away. I turned it out 1/4 turn, and it works great. I still have a 160 main, and clip on third notch, and 42 slow jet. Why would turning in the airscrew fix the bog? Did this richen the mixture, or lean it? I think the screw should be out more than 1/4 turns. It use to be two turns out, and I never tried turning it in more than 1-1/2 turns before I assume that I need a different airscrew, but which direction should I go.

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I'm assuming you mean the fuel screw? If so, turning it in makes the pilot circuit leaner and turning it out vice-versa. From what I understand it's sort of a fine-tune for the pilot jet. Further, I believe the recommended range is 1/2-3 turns from all the way seated. Generally speaking, any lower than 1/2 turn out and you need a leaner pilot jet and any higher than 3 turns out and you need a richer pilot jet.

Here's a good article on the subject: http://www.thumperfaq.com/fuel_screw.htm

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The bog caused by cracking the throttle open can be reduced by changing the leak jet. The leak jet adjusts the output of the accelerator pump. Try installing a #55 leak jet which will increase the accelerator pump's output when you crack open the throttle. Note that a smaller leak jet results in larger accelerator pump output.

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