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Crf250x hesitation in quick throttle opening

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I have a 2006 crf250x that has an fmf megabomg header and fmf q4 slip on. Other then that the bike is stock. When i crack the throttle quickly it has a bad hesitation especially when its cold. I have considered buying the jd jet kit but dont know what size jets to use. I ride at 600 to 1,000 feet elevation. If you know what size jets i should use please let me know. Thanks!

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i had the same problem on mine. youre definitley going to need to change the jetting because right now you're running too lean which means there is not enough gas getting to your engine. I have the same setup and we are around the same elevation as well.  I believe the stock jetting is a 130 main with a 40 pilot jet. I run a 142 main and needle clip on the third position with the air screw about 2 1/4 turns out with a 42 pilot. however I also opened up my air-box to get some extra flow going on. the bike seems happy as am I. I pull the spark plug every now and then just to keep in check that its a nice brownish color. jetting the carb is easy. the fun part is actually getting to the carb... the stage 2 jd jet kit comes with all of what you'll need with some good instructions as well. goog luck man hope this helps somewhat!

 

ps. also search for a guy named rick ramsey on google. he has his own website thatll tell you everything you need to know about crfs!

 

 

-Rick

 

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Quick throttle bog (by it self) is not a jetting issue.

It is an accelerator pump issue.

 

Granted, if you are factory jetted and factory corked up, you are a tad lean, and any opening of intake or exhaust makes it much worse.

 

 

 

A JD jetting kit, following the instructions, changing your leak jet to 55, changing your apump linkage spring to a Tokyo mods spring, and making sure your diaphram and apump nozzle are working (visually inspect the 'squirt' ) is the trick.

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Just curious, what is the reasoning for suggesting the JD kit over OEM needles?

 

Easiest way for newbie carb tuners.

 

I could go into tremendous detail about how to get the most from that carb, but it will seem odd to somone who has not even uncorked their bike yet....

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Simple fix is a #78 oring on the pump arm. Spring more permanent , but both work.

 

o ring edit.jpg

 

 

the 06 x has it's carb roots from the 04/05 R. The r uses a bigger bypass (leak) jet.  So the spring that drives the pump arm doesn't have as much load on it as more fuel is bypassed instead of going through the tiny squirt nozzle.  The X squirts more fuel (using a small leak jet) so the spring is borderline adequate in tension.  Why the stiffer spring or o ring mod recommendation.  Any kind of test for hesitation or bog should only be done while riding and good warmed up motor, not cold.

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Thanks for all the help guys. I ordered the jd jet kit and did the o ring mod and it runs great now. No backfire and very little bog. Im using the 165 main jet 42 pilot and the red needle on 5th from top. Not sure the amount of turns on screw though.

Edited by Ben_Williams52

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