YZ426 Low rpm Hesitation

I agree with these guys, clean the carb. Mine has done the same thing in the past, a carb cleaning fixed it completely. Tweaking the fuel screw is also great advice.

Thanks, I will give it a try tonight.

I have had my 2001 yz426 for about a year. It is a great bike and I have not had any problems at all until just recently. The bike is completely stock except for a FMF Powercore IV. About a week ago I started noticing a low rpm hesitation or what I call bogging down. It just doesn't seem to have the snap it use to when you first punch it. Once you get moving it is normal. The only thing I could tell is that the hot start button sometimes doesn't stay out when I'm starting it. It may be bent or a little gummed up, but looks fine from the outside. I take good care of the bike and do all the maint. If anyone has any insite I would really appreciate it.

Clean the carb.

Yep - the first place to start is to take the carb off and clean it up pretty good. I take all the jets out and spray them with carb cleaner, make sure the slide moves up and down nicely, check the float bowl, etc.

Your pilot jet (under the float bowl) or pilot air jet (under intake bell on airboot side) may be gummed up a little.

Also, you didn't say that you adjusted your fuel screw at all lately. Considering the hot weather in Texas now you should be turning your fuel screw IN (leaner) to compensate for the weather. You might just try that first. If you turn it in and the idle starts to "hang" but you still have the "bog" then go to the next smaller pilot.

Clean the Carb and clean the seat

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