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Hope one of you guys could help me with this one.. my buddy has a 2004 400EX (I have a 2002) and he hasn't run it in about 10 months. When he started it up it wouldn't idle and you'd have to feather the throttle to keep it running as it would want to die. However, if you turned the choke on it would temporarilly solve the issue but then it'd be running too rich obviously.. So I went over there to clean out the carb assuming it would fix the issue.. I cleaned al the jets and accelerator pump with carb cleaner and blew everything out with air. Still not fixed.. so I read the manual and it mentiones the Air Cut-Off Valve and how a vacuum issue could cause these symptoms.. Does anyone have any other suggestions on what to look for/clean since everything I did didn't help..? Or have you heard of the air cut off valve being the issue? I pulled it apart and it seemed OK but I didn't have a vacuum pump to test it..

and yes, I drained all the gas and put fresh gas in..

thanks--
 

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Welcome to the site. Is the petcock cleaned and clear?
 

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Welcome to the forum.check the air filter and did you run a wire through the jets to clean out all the gum in them sometimes air and cleaner along wont do it
 

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I believe he said he did, he just didn't have a vaccum pump to test it.
 

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you must still have a piece of trash in your idle circuit, I just cleaned out a carb from an 85 atc110 that wouldn't idle and that was the issue. the slow jet was stopped up but the end was flowing through all the holes in the end. check that again. also while its running spray some w-d40 around the gasket to make sure your not leaking air. then check the rubber boots to the carbs they may be cracked.
 

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Hope one of you guys could help me with this one.. my buddy has a 2004 400EX (I have a 2002) and he hasn't run it in about 10 months. When he started it up it wouldn't idle and you'd have to feather the throttle to keep it running as it would want to die. However, if you turned the choke on it would temporarilly solve the issue but then it'd be running too rich obviously.. So I went over there to clean out the carb assuming it would fix the issue.. I cleaned al the jets and accelerator pump with carb cleaner and blew everything out with air. Still not fixed.. so I read the manual and it mentiones the Air Cut-Off Valve and how a vacuum issue could cause these symptoms.. Does anyone have any other suggestions on what to look for/clean since everything I did didn't help..? Or have you heard of the air cut off valve being the issue? I pulled it apart and it seemed OK but I didn't have a vacuum pump to test it..

and yes, I drained all the gas and put fresh gas in..

thanks--

i need the rubber boot that goes on the shaft of the accelerator pump. any ideas?
 

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Yeah, sounds like you still have something in one of the jets or air passages. Did you pull the float out and clean the needle valve and seat and blow the hole out with an air hose? Sometimes it is easy to miss one of the tiny air passages. Carbs can be a pain sometimes.
 

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Check the tank vent.
 
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