I just purchased a 2000 400EX. Over the last couple of months, I have been reading up on a lot of information in this site on the 400EX.
I am totally clueless about doing any tuning enhancements to the machine. One area I am concerned with is the fact that the 400EX is known for running lean from the factory.
How do I fix this? Do I need any special tools/testers to fix this? How will I know if I've taken care of the problem? I think it runs fine as is, and I have a hard time fixing something if not broken. I'm at sea level and probably don't go above 1000' Thanks in advance.

 

Don't believe everything you hear in these forums...that's a bunch of crap. If you pull your plug, you'll notice a nice rich color...white is lean and it won't be white! There is no need to rejet a stock machine until you start adding mods. If you have great response at full rpm's in fifth gear, don't touch it. If you do anything, adjust the throttle cable to it's full potential...(correctly stated in here a few weeks back by several people).

BTW, I'm in no way busting up on the forums...just keeping a fello rider on the right path!

 

briancwatkins,
There's a twist on the old saying you referred to;
don't keep fixing it till it breaks!

 

Thanks fellas. I have in fact seen the throttle adjustment post, but just haven't gotten around to actually adjusting the throttle. In reference to the "lean" issue, I wasn't sure if running it lean would create problems later. Plus, the **** part of me likes things the way they are supposed to be. With that said, I will leave it alone.

 

Easy there, before stating that something is "crap". Take a look at your owners manual, I don't have mine with me right now, but I believe it's on page 143. Honda themselves states that it is jetted lean.

Do you want the EPA jetting your bike? I don't. But that's exactly what has happened.

Now, that doesn't mean the 400EX is jetted lean for all situations, heck, it may be correct for some climates and altitudes. But when a manufacturer states directly that the bike is jetted lean, it's worth some attention. Even if they don't, jetting is worth some attention, especially on a 2 stroke, as the factory cannot custom jet each bike for it's intended destination. BTW 2 strokes are usually jetted rich as a safety factor by the factory....

What color are your header pipes? Have you put an EGT on your header?

BTW mine IS lean. It is stock and I am at about 900ft elevation. My plug is whitish grey on the tip with black carbon on the outside (It gets ridden pretty hard, so I assume that's oil carbon as it doesn't look like rich fuel carbon), and my headers are quite purple and blue. Unfortunately I haven't had a chance to rejet it yet, but am going to in the near future...

 

Brian,

Check your throttle now! I posted the original "throttle" thread back in September, and just about every 2000 400EX owner I have come in contact with since has found the problem on their bike. Free horsepower is the best kind... e-mail me if you need any help.

Now, check your jetting via plug read, EGT, etc... As I stated before, mine is bone stock and is lean. There is more to jetting than just wide open in 5th. The lean jetting will cause your engine to run hotter than it should, and make it hard to start when cold. There are some people who think the 400EX is too rich because they have fouled plugs when trying to cold start. But what many don't realize is that the 400EX is the only mainstream ATV I am aware of that has an acclerator pump and will flood the bike if the throttle is "pumped". My thinking is that Honda did this to mask the "lean cruise" condition mandated by the EPA.

Good luck...

 

Wow! My head is spinning a little now. Some say do...some say don't. Luckily, I am easily swayed. Plus, as mentioned before, I’ve seen an awful lot of posts about the machine running lean. Actually, I even remember reading something about the manual stating that it runs lean, but forgot about it.

GABE: You mention "plug read" and "EGT"??? Is plug read as literal as you mean it...actually taking the plug out and inspecting it for color? And EGT...have no idea what this is. Like I said, I AM CLUELESS, but not incapable of learning more about my machine. Your help is appreciated. I’m in the DC area, so I am guess I am pretty damn close to sea level and I doubt I go above 1000’. Thanks for the info.

 

Brian,
In fact, Gabe does make some very good points and that's what we're all in here for. Take some time and educatate yourself and absorb as much info you can by asking questions and reading up on your needed issues. An excellent site is HondaEX.com. There, you will find tips on reading your plug, jetting etc. as well as several different topics on the 400ex. Start by yanking out the plug and checking the color...white is lean, black is rich, and "well done marshmellow" is perfect. Let us know and we'll give you the help your looking for.