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crf hesitation issues

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Hi all, been reading posts on here for years but never made an account!

have a couple questions I have a 2005 crf450r and my girlfriend has a 2006 crf250r. both bikes Ive jetted and they run great however they both have the same issue when revving on the stand. If you blip the throttle quickly it will bog for a second or just cut out. when revving you kind of have to roll the throttle to avoid killing it. its driven me crazy for years but they dont act like that at all when riding.

Any Ideas? 450 has the boysen accelerator pump. 250 has the boysen qs3 adjustable accelerator pump.

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Perfectly normal. The carbs on these bike are fairly large. When you nail the throttle at idle, the vacuum signal (the sucks the fuel throught the jets in to the engine) is week. Take a paper towel tube. Cover all of it except a tiny gap. Suck on it, then sussenly remove the cover, you'll see what I mean. Take the same tube, open the opening a little and you'l see the vacuum remains somewhat strong. You carb has an AP that helps with this vacuum loss by squirting a bit a fuel in the carb when you hit the throttle. Just at idle, you are simply asking too much of it. If your problem only happens on the stand, who cares? What matters is how it performs under normal riding conditions.

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yeah that's kind of what I figured, we have a 2010 ktm and it doesnt do it on that bike though so I was wondering if there was somthing I was missing!

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You can... tweak the jetting so it will accept a handful off of throttle at idle but... the trade of is the AP will dribble fuel almost all the time (any wrist movement) and when you are at say 3/4 throttle and hit it, the AP will be way rich and you can have the opposite, a rich/8 strock bog.

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