Hello. I have a stock 2001 - 400EX and I have extra money to put on it. My firsts choices are as follow:

1) K&N Air Filter
2) Dynojet Jet kit
3) 16T front sprocket

Do you think my choices are reasonable for the first mods? Do you have another opinion? I am 23 years old male, and I run for fun, I don't do any competition and I am not a pro neither. I just want to ride and have fun with friends!

Thank you.

 

Are you sure about the 16 tooth sprocket. It might hurt you if you like to hillclimb. Other than that it would probably ok. If you are just going to change your air filter go up one size on the main. If you are going to mod your airbox go up two. Main jets are only about $4 a piece. I think you could save your money just buying a few jets over buying the Dynojet kit.

Adam Smith

99 400EX

 

Take adam's advice and do not get the jet kit. Just buy the main jets from the honda shop 152, 155. You can get away with stock jetting with a pipe and an air filter. I bought the dynojet kit and I got a lot of jets that I didn't need and I am running a Kehien jet 160 anyway and that is with a lot of mods.

A 16T front is going to give more top end speed and less on the take off. If you find that you are riding in 4th and 5th all the time, this would be a good idea, BUT, I don't think the case saver fits a 16 tooth sprocket and you definatley don't want to run without that. I run woods so I am usually running in 3rd and 4th and I dropped to a 14T on the front.

Good Luck

Nick

99 406 EX

 

Thank you guys. Very appreciated. As for the jets, I have no idea if my configuration will change soon or later, so I prefer ordering the kit in case the jetting need to be changed. I also want the instructions to make sure the guy that do it will do it correctly (I know nothing about mecanics). As for the sprocket I think I will drop the idea, it look like it is not what I need (I do ride steep hills and run 2nd and 3rd mainly). What the 14T sprocket do? does it give you more power in lower gear?

 

m1ckey78 -

To get you started off on the right foot, you should really take a look at the Tech Connection here on this site. From this link just select "All Models" and "Carburetion/Jetting/Fuel System." If you work your way through the questions and answers, I think you'll learn quite a bit and gain a better understanding of jetting and modifications. In fact, its quite likely that you may feel comfortable just doing your own jetting (trust me, its LOTS easier then bringing it to a mechanic!).

The other folks are right, don't buy a jet kit, its a really big waste of money. After checking out the tech connection, searching through old posts and asking questions - you'll see that jetting is a snap.

Last, The stock air filter on the 400ex is quite good - but if you really want an aftermarket filter you should look into a uni filter (foam). I have a K&N air filter right now, with a K&N pre-filter around it. The pre-filter is all but shot, because it rubs against the airbox when riding, leaving little rips in it's seams.

One other really big thing that you should check on, see if your throttle is opening all the way. Honda has been sending these machines out with too much play in the throttle. You could gain quite a bit of power for free.

This is a quick way I've found to check if the throttle is too loose: Stand next to your quad (not running), put your ear up to the throttle housing (square thing right above your thumb throttle), and rapidly push the thumb throttle as far as you can. If you hear a "click" noise as it stops (coming from the throttle housing), then you know that the thumb throttle housing stopped it. That means you have too much slack in the cable. You should adjust it til it has about 1/8 inch of play before it engages.

If instead, you hear the "click" noise from the carburetor area, you know that you've maxed out the carb's travel - thus is adjusted correctly.

Hope this helps,
ogre

 

Very interresting, especially the trottle thing, this is the first time I hear about that. I unmounted all the fender yesterday night, this is easy to look at everything that way.

You guys have good opinion, and I decided to go with the K&N Air filter with the whole jet kit. This is a birthday gift from the girlfriend, so I dont really mind about prices. (I always bought here big gifts before.. so this is her turn now! ).

I heard a pipe is almost useless on a 400EX. Not much to gain from it. Is this true?

 

You're pretty much right, m1ckey78. If throwing on a pipe and air filter is about all you're going to do, the pipe is basically worthless. I've seen countless dyno readings from the mags, and other people pointing to the fact that aftermarket pipes alone rarely even help a little.

After making internal modifications to your engine, adding a pipe does make a bit more sense. You have to remember, however, that your machine will be considerably louder with an aftermarket pipe; this can be an issue if you ride in a noise-sensitive area.

Gabe, on this forum, has created a few diagrams showing how to modify your stock silencer - the claim is that it will give you increased air flow while not drastically increasing sound levels. Click here for Gabe's diagrams.

Actually, one of the best modifications you can make to your 400ex is to bore to a 416 and increase your piston's compression (10.8:1 - 11:1). If you search the keyword "compression" or "je" (the piston lots are using) in the honda forum you'll find plenty of info regarding this modification.

ogre