400ex running really weird

[jackrb100]

Ok I just rebuilt the tranny on an 04 400ex. After I rebuilt it it ran well just ticking over in the garage and went through the rpm range fine. But now after a couple of carb problems I have ended up with this kind of problem. When I start the bike with the choke on it runs quite ok wer I have the idle currently set but if I try to go to WOT it runs really rich and pufs black smoke and trys to die when I turn off the choke it revs really high and with the idle as low as possible it doesnt change. Originaly there was a pipe disconnected on the carb that when I put my finger over it the bike ran better so i put it onto the thing under the plastic bit on the carb. Im confused and hope sombody can give me a second opinion im not furmilior with the 400ex. Bike is bone stock.

Any help would be great I'm having the same problem

[2001400exrida]

do you have stock jets? check your a/f screw and make sure it's not turned all the way in. also, what did you do the carb or what problems did you have? it may need a good cleaning. does it run better with the lid off? take your lid and air filter off and hold your hand over the intake. see if it will run better or worse.

Originally posted by 2001400exrida
do you have stock jets? check your a/f screw and make sure it's not turned all the way in. also, what did you do the carb or what problems did you have? it may need a good cleaning. does it run better with the lid off? take your lid and air filter off and hold your hand over the intake. see if it will run better or worse. Mines bone stock. Stock jets, I just cleaned the carb really well and it helped the idle. I'm just wondering why mine is idling so high once it gets warmed up. I haven't had time to mess with the idle adjustment yet

[2001400exrida]

you can turn the idle adjustment down when it warms up, but you need to be able to get it started and get it warmed up with out having to adjust the idle at all.

Mine sometimes needs messing with but once i get it locked in, i don't have ot adjust it.

[jackrb100]

Jets and everything is stock. The lines around the carb were on wrong to start with and I have already cleaned the carb. Does anyone have a picture showing were all the lines go? I have a feeling they are the problem.

Originally posted by 2001400exrida
you can turn the idle adjustment down when it warms up, but you need to be able to get it started and get it warmed up with out having to adjust the idle at all.

Mine sometimes needs messing with but once i get it locked in, i don't have ot adjust it.
Wheres it the idle adjustment at on the carb? left side right? It warms up fine with just the choke, once it gets warmed up it seems like its idling too high and 1st gear seems shorter

[2001400exrida]

idle adjustment should be facing the left side of the quad. the shifter side that is.

it's just a silver flat head bolt. It's normal for the 400ex to idle real slow when it's cold so if you're idle adjustment is set to high you probably just need to get the quad warmed up and then turn it down until you find a good idle speed.

1st gear is short btw, it's not to fast haha.

[jackrb100]

Does anybody have any info or help regarding my original post? Thanks for the replys so far. I need this bike running properly asap.

[01 400EXer]

What is your air filter set-up. I only ask this because I have a Outerwears pre filter and when that gets oily and dirty, my 400 start to run really rich,hard to start and takes forever to warm up, but it does a good job keeping the filter clean. It is already jetted for an HMF pipe and holes in the air bix lid.

[jackrb100]

Everything is entirely stock. The bike has only done this since i put the carb back on so i am sure its something that i did with it, its just a matter of figuring out what ive done wrong. Im still thinking its something to do with the lines that run around the carb up top. Im sure its something simple. Thanks

[01 400EXer]

Could one of those vent lines be pinched?
Not sure if this will help you.

http://www.cheapcycleparts.com/model_years/1243-honda-2004-trx400ex-TRX400EX/assemblies/13651

[jackrb100]

Don't think so but i will check tomorrow when i am at home. Thanks for the responses.

[Crazy Bob]

Hey,
One other thing you might check for to get it to idle slower.
Make sure you have some free play in the throttle cable. If the cable is too tight it will idle too high even if the idle speed adjust screw is backed all the way out. Not knowing more about your specific carb problem, I don't have any other comments.
On another note. I see alot of problems after people say they :"cleaned their carb". Carbs are fine instruments. Float settings, pinched gaskets and O-rings, and tiny pieces that are dropped or fall out unseen and never get put back in.... Use fresh, clean gas. Carbs usually do not just "Go Bad".
Not Everyone Should Be Dis-assembling Carbs....

Ride Fast, Hvae Fun..
Crazy Bob

[Honda4LifeWes36]

x2 with crazy bob. I've had my fair share of dropping those small pieces in a carb. That one little piece could mean it all from running good to running bad.

[backwoods 400ex]

to get like carb diagrans sites like bikebandit.com and atvparts.com have diagrams

[jackrb100]

Hi again, since last time ive gotten the bike good. The only problems now are that when I go to WOT the bike puffs black smoke. Thanks for the replys guys they are much appreciated keep them coming.
Thanks