400ex cough or hickup

[cocopot2002]

I have a 2002 400ex having some kicking, coughing, hickup, whatever. I don"t even know what to call it, like a bump while at idle, can"t tell if its coming from the carb or cylinder, sometimes it will kill the engine , if I give it gas it just bumps, stalls a bit and runs normal, seems like it does it bad until it warms up and then not as bad. the bump hits hard enough that you can feel it in the carb, kinda like its got pressure in the system somewhere and trying to push it out. anyone know what i'm talking about?

[bencasey217]

I'm pretty sure its suppose to do that, mine has done it for three years. I'm pretty sure nothing's wrong with your fourwheeler.

[cocopot2002]

That's a relief. Thanks for the help.

[CJM]

Mine does it ever so slightly and always has since I have had it.

Id try cleaning and jetting the carb properly. The pilot jet from the factory is WAY to low, most need a 40 or 42 pilot. Also if you have done any modifications you might want to reject the main jet as well.

[cocopot2002]

I wondered about rejetting for a whites brothers slip on that it had when I bought it, the guy I bought it from didn't do any jetting at all on it to compensate. I cleaned the carb out yesterday and checked all my o rings and jets to make sure they were all clean. what size main should I go with if I changed the head pipes out with FMF's with a power bomb, and added a K&N filter?

[CJM]

150-155 main

[Drfat400ex]

My main is too rich and if you're at idel while in gear and give it more than 3/4 throttle it boggs. idk if that might be your problem or not.

[cocopot2002]

Do you know what the factory carb is for the 400ex? My main has an adapter on it. What kind of jets do I order? Mikuni or kenin?

[CJM]

148 is stock, sounds like you get a dynojunk kit installed. Throw it away and buy keihin main jets.

[cocopot2002]

Will do. Thanks.

[cocopot2002]

What brand of jet does honda use in that carb that they have to use an adapter?

[JOHNDOE83]

A cough or hickup is generally a lean condition, especially if it happens threw the carb, or your idle is set to low.

www.jetsrus.com < check out the FAQ section

[cocopot2002]

Ok, thanks