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yz250f 290 big bore jetting

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most likely rich if the pilot is stock. A 290 will create more vacuum when the throttle is closed, thus pulling in too much fuel from the stock pilot.

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If its bogging when accelerating then look at your accelerator pump circuit. Make sure it's squirting, if it's squirting then go to a smaller leak jet and do the o-ring mod.

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O ring mod it easy, try that first, but usually in my experience you want to go down on pilot jet with a BB KIt.

Very good looking bike. With that recluse and 290 you have a secret weapon.Make sure you dont jet it too rich or it will be a SOB to start hot in the woods, trust me I know 😉

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O ring mod it easy, try that first, but usually in my experience you want to go down on pilot jet with a BB KIt.

Very good looking bike. With that recluse and 290 you have a secret weapon.Make sure you dont jet it too rich or it will be a SOB to start hot in the woods, trust me I know 😉

Yeah I know what your saying! So i've tried the o-ring mod and it doesn't seem to do anything as far as the bog. I am going to get jets today and will update with the results.

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Make sure you dont jet it too rich or it will be a SOB to start hot in the woods, trust me I know 😉

LOL, yes, a rich jetting when hot will just about kill you trying to restart in a race.

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Hey, I tinkered with the jets and ended up with a 165 main, 40 pilot, and 3 turns fuel screw. It still has the factory leak jet but now the o ring mod seems to have helped. The bike can be idiling and I can punch the throttle wide open and it only has a slight hesitation then it revs right up. It runs WAY better than when I started and I'm sure I'll tinker with it some more!

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Hey, I tinkered with the jets and ended up with a 165 main, 40 pilot, and 3 turns fuel screw. It still has the factory leak jet but now the o ring mod seems to have helped. The bike can be idiling and I can punch the throttle wide open and it only has a slight hesitation then it revs right up. It runs WAY better than when I started and I'm sure I'll tinker with it some more!

next, play with the needle clip. I'm betting leaner will work better. Pay attention to the bog while riding. Blipping on the stand isn't an indicator. If you get a bog when you're 3rd gear out of a corner, try rolling on the throttle and see if you still have a bog. No bog on roll on, then change the LJ.

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I have an 07 wr 250 with the athena kit it had some bogging issues too, just installed a JD jetting kit today and man what a difference! one thing you may want to try is a heavier (thicker) o ring on the oring mod I swapped mine out and it made a decent improvement in the lower end. good luck sounds like you're on the right path though

oh and here's a site that helped me out a lot its got an amazing chart for figuring out which jet is off..

http://www.4strokes.com/tech/carbover.asp

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i recomend second clip pos from top on the needle 42 pilot and put the screw at about a turn and a half for starters and about a 178 main and open the air box top.i have run the 290 kit and jetted a few yz250f bikes in the pacfic north west mostly 03- 05 bikes so i segested slightly leaner for you in georgia on main and pilot than what i run.

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