ex400

[shaunwhite]

:( :( my 400ex keep filling the engine case with gas!! ill clean it out it will run great for about a day. then next time i use it. it will fill up the engine again till gas into my air box. help i would like to go riding this weekend???:(yes you are right about turning the gas off. but it should not fill the crank case full of gas yeah. i did check the float. it is with in spec. as per honda.

[honda8&3]

Bring to a professional quad shop. Have them fix it. Then sell it and buy a different 400ex.

Whats and ex400..LOL:devil:

[Dill]

probably a stuck float in the carb. As a general habit you should also shut your gas off when you're done riding for the day.

[400exrider707]

Originally posted by Dill
probably a stuck float in the carb. As a general habit you should also shut your gas off when you're done riding for the day.


I doubt it would "run great for the day" if the float was stuck though... it makes no sense to me, and part of the reason is his question is so hard to read.:confused:

[GPracer2500]

Float or float valve problem is the most likely answer.

If it's a slow leak (at the float valve) then it probably does run fine--as long as it's being run. But as soon as it has a chance to sit, that slow leak as the time to empty the tank.

[shaunwhite]

float valve???? will i have to replace it??? have you ever seen this problem???:rolleyes:

[GPracer2500]

The float valve is the thing that allows fuel to flow into the float bowl when the fuel level drops. When the fuel level raises to a certain point, the floats raise up and closes the valve.

Here's a pic of a float valve assembly. The part with the rubberized pointy end attaches to the floats. It fits inside the float valve seat (the other part, which is pressed into the carb body). Pull the valve out some and fuel flows into the bowl. Press it in and that rubberized part presses against an orifice in the valve seat and stops the flow.

http://www.armor-tech.com/images/Misc/CR252.jpg

I don't think the float valve seat is replaceable on the 400EX carb. I'm not 100% sure on that though. But the other part is replaceable--as is the float itself. As long as there are no pin holes in the float--making it not float--it should be ok.

First thing I'd do is remove the carb, disassemble it, and clean with carb cleaner and compressed air. Could be that there's just some gunk on the valve preventing it from sealing. That's not uncommon.

While the carb is off the bike and the float bowl is off, you can hook up a fuel line and inspect the function of the valve. Lightly push up on the float and observe if the fuel supply is cut off or not. You don't have to press hard on the float. The valve has a spring loaded plunger on one side (see the little rod sticking out of the left side?). You only need to move the float upwards until just before that plunger begins to compress. If you press hard on the float, that plunger will compress and it may force the valve into it's seat and stop the flow--but that's not the amount of force that it will see just from the float raising in the bowl on it's own.

The float has a specification for the point at which it cuts off the fuel flow. It's 18.5mm. That measurement is obtained by measuring the distance between the outermost point of the float and the sealing surface of the float bowl. The measurement should be taken just before the float's tang compress the plunger on the float valve. Kind of hard to describe, but these pics may help:

http://www.cartestsoftware.com/fz1/images/rulerplacement.jpg

For the 400EX, the correct measurement is 18.5mm, not 21mm.
http://www.dfn.com/benkaren/floatadj.gif

The tang that connects the float valve to the float is metal and adjustable on most floats (like it is in the above picture). Not the case on the 400EX carb. So if the float height is off for some reason the only recourse is to replace the float.