Hey guys, I was wondering how I could make my 400ex faster? It is all stock except for nerf bars. It is an 04 400ex. I recently cleaned the air filter, but I would like to make it so it is faster.

Also I was thinking of maybe getting a TRX450. What are your guys thoughts/comments on this bike?

Thanks, I appreciate the feedback.

 

If a TRX 450 is in your future, save your money and leave the ex stock. If you plan on keeping it, simple things like exhaust, ,a free flow air box lid cover, a quality aftermarket filter, rejetting Honda is very lean from factory, go up one size on pilot, mains will depend on what you run for exhaust and intake. Honda factory pipes and mufflers are very restrictive, so just adding that will make a big difference. You will also want to get a +1000 rpm CDI, with the motor breathing better, it will rev quicker and higher, and you will be bouncing of Honda's famous low rpm rev limit. If you look on eBay, you can find these parts fairly cheap, sometimes even good used stuff shows up for even less. I would leave the motor stock unless it needs a rebuild, it will last a lot longer in stock form than a bored out one.

 

If your going to be a casual woods rider yet get agressive for fun now and then, I'd stick with the 400ex. They are more dependable in the long run than the 450.
The 450's do have a bearing/crank issue sooner that most like.
400: get a mid cam and good pipe. That will wake the motor up. A previous reply mentioned parts, they are a good idea too.
To go fast, it takes a superior suspension. This is where to put your money to go faster!
FYI: GTThunder is known for having about the best stock shock rebuild. If ya have bucks, don't mess around and get PEP's

 

i put cdi and dynojet stage 1 in my 04 400ex and i saw a big difference. think I'm going to get an exhaust next

 

PEPS? What do you mean by those letters?

Not sure if referring to aftermarket suspension, rebuilt...


Would someone recommend brand names/ stores with the recommended mods, besides Ebay.

On the level of difficulty, How bad it is to install a cdi?

 

PEP is a brand of shock.
CDI replacement is about as easy as it gets. Unplug and remove. A stock XR 250r CDI will give you about 800 more rpm for about $25. If you want quick and easy speed just regear. Going from a 14tooth front sprocket to a 15 tooth will make a noticeable difference.
Good brand names for the ex are - hotcams, cometic, powroll, wiseco, jt, anything from gtthunder. I get a lot of stuff from rocky mountain atv. I have had very good luck with rmatv's tusk line of parts.

 

Thanks for the info, I am trying to find a chain master link for the 400ex 2007.

From what it seems my chain is a 520x94, seems to have a hard time trying to find the master link. Have seen 30 dollars or so, unless it is the chain been sold and not the master link.



For the CDI I found the EK Racing CDI Rev Box for Honda XR 250r, it states it will only fit those models, Will it still fit the 400ex, and is it worth the 20 dollars more?



It states on some sites to change the chain when changing sprockets, is that really necessary?

And its incredible how many stores are out there, will try out rockymountain.

 

Iam not 100% sure but I dont think the stocks chains had master links. When you buy a chain they come with a master link. Its a good idea to change the sprockets with the chain. I replace my chain and sprockets every year. When you compare the new and old you will see the difference.
The ex doesnt make good top end power. I dont know many ppl who run a aftermarket cdi with a stock motor. If you are looking for a magic box to make you faster, your not going to find it. If you want to go faster and dont want to tear in to motor look into suspension upgrades and mess around with the sprocket sizes and tire sizes. Remember gearing changes is give and take. When you gain speed you loose torque and vise versa.

 

Is this a slip on muffler?

Sorry for my ignorance, but not sure what it means. That one is around 270.



Here is another mufler, 275 for that one. Not sure with which one go and if price is right.

 

Yea those are just the slip-ons.... The HMF pipe is the more preferred pipe, it's a moderately loud pipe. It has a real nice tone to it.

The hmf is worth the extra $5, if you were on rocky mountain atv's website looking, they also have the new hmf competition series slip on.... (with differant inserts... )


Dyno charts: