I have a 400 with a full system and one with a slip-on and they both seem pretty close to me. The one with the slip-on feels stronger though. Exriders.com has a ton of 400ex tips. You can use the search feature or go the FAQ and you will get a ton of advice. Some of them will be to remove the choke and grind the header welds.

 

hey DRIP, sorry to offend you with the reply I sent for a little info....... a simple I have....and, it works like this... would have been great from ya though........

 

MrMonk or whatever if you want a little more rev in each gear you could get the white bros rev limiter you can see it on most sites i saw it on Rocky Mountain Atv most places are from like 92 to 102 bucks. It runs the stock 9300 rpms to 10300. I dont know if this would interest u or not but noone else suggested it

 

<< for one a rev limmiter cdi is a joke ! dont waste your money ! the power curve of a 400ex drops off before that rpm any way ! it may sound faster but it isint! this is the best setup for a 400ex that you dont touch the inside of the motor!

lrd full system exsaust
k&amp;n filter with outerwear (yes k&amp;n)
airbox cover removed
snorkel tube removed altho you need to plug the hole ! causes turbuloance !
choke removed from carb (jb weld hole or install a hose over it and plug it ) ex dont need choke it has a acc pump,just pump the throttle and start it )
dynojet kit (yes get the jetkit it contains the right needle you need ,and the right p jet
also for more topend speed you can swap out to a 16 tooth front sproket and shave the front fenders off for a good 7mph gain >>



You actually loose power with the LRD full system on a stock engine...
K&amp;N sucks...been there rebuilt that....
With the minimal gains of fully removing the airbox, it's not worth it to a novice racer
The dyno jet kit...there's a classic money making scheme... First off, the needle supplied will give you a bobble in the throttle just as your entering the half throttle point. And you don't need the extra, oh say 5 main jets in the kit.

Bottom line. For a guy that just wants to add some more power to a quad that is going to be trail ridden and occasionaly raced....stay away from opening up your airbox completely, running a Air Filter that sucks dirt, getting schemed into thinking you need the Dyno Jet kit and stay away from a full exhaust system. With the money you save, spend it on skid plates and put some towards suspension upgrades. Suspension upgrades is one of the most overlooked subjects in making a person able to ride faster over various terrain....better suspension will make you a faster rider, I guarantee it.

 

I'll see if I still have the dyno sheets there tough guy. I'm not saying I know everything, but I'm sick and tired of Racers telling rec riders how to mess up their engines. We don't have the resources that you guys have. Yeah, a K&amp;N might flow more air, you'll suck more air by removing your airbox lid and tube, but the reliablility just went down on his engine. He's not tearing it apart after everyother race and re-building it or what have ya. Just try to think of that when you post....

K&amp;N Number 1 ??????? LOL!!! I've never seen that! Tell me another one after you pull your filter, and see how much dirt is in your intake tract. And I want a picture too! And I didn't say anything about a airbox....an airbox lid though.

 

I've yet to witness a stock 400ex run right with a Dyno Jet kit....and I've belonged to a 400ex E Group for 2 years with over 100 members...so don't get cocky with me. I've read/witnessed alot with a 400ex. I don't think there isn't a modifacation short of a turbo charger that we haven't tried. Countless hours of testing of products has lead us to believe the facts. And the facts are K&amp;N filters pass dirt into your engine. Proven Fact! Christ right on the package &quot;as dirt builds up on filter, filter will perform better....hence, not allowing as much dirt into your engine.
Proven fact #2 Dyno jet kits do not add power to a stock engine! And main jets are $4.00 a piece...so one for the winter one for the summer, I'm out....$8.00.

And you forgot to mention that you need to raise your pilot jet when you remove your choke also...

 

And wipe your finger in the tube and look at the dirt on your finger. It'll be a fine dust.

BTW Biggy, now I remember wasting time trying to talk to you before.....

Good ol Gabe will give you a nice story about a K&amp;N filter and a day at the dunes.....


BTW, how'd that magnafluxed head work for you!? LOL!

I'm done with you.

 

Bartlett racing i went to your homepage nice pics. Where did you get the graph with those top speeds of the quads. Did you make it yourself or is it a tested graph? Thanks

 

<< for one jvc magnafluxing the head test's for cracks ! it's not a performance thing at all ! you might try sitting back ,shutting your mouth ,watch ,and learn a little... first leason .http://www.knfilters.com/facts.htm ......Read up ! k&amp;n filters dont damage motor's ! the owners do! >>




Yeah, and aluminum is very pourous.....doesn't work too good. I know this from working at a powder metal factory for 8 years.....

So go back to living in Biggy's world, i'm doing fine over here in reality!

Hey, I can write up a heck of a marketing segment to mice about how nice cats are too....doesn't matter!

Anything else Biggy?? Besides a big pile of Bullsh!t?! HMMM???

 

Here are some ideas for cheap mods for an EX. I've done 3 other friends quads and so far everyone is very happy. Try it and see what you think. Not much cash involved and just a couple of hours of work. These include silencer mods, air filter and airbox mods, a slight shange to the snorkle, and some jetting.
After removing the silencer from the quad go ahead and remove the 3 8mm bolts and pull the spark arrestor.
Towards the front of the silencer you will see some spot welds that the factory made. Using a 14in chopsaw or a sawz-all, cut the silencer in half just in FRONT(meaning towards the front of the quad) of those spot welds. It helps to scratch or centerpunch 2 marks on either side to help re-align the halves later.
Using a Dremel or a small cut off wheel, cut the pipe off as far down into the &quot;cone&quot; or &quot;funnel looking piece&quot; as you can When you look into the cone shaped piece you'll see the part that needs to be cut off.
Next, using a drill bit in the large variety(13/16,15/16/or 1&quot drill three holes in the inside canister from the back as if you were looking into the silencer from the back. Your bit should be long enough to reach in and drill the holes . The metal is not thick. Do try and line up the new holes w/ the tubing that runs thru the inside canister.
Next put the spark arrestor in the chopsaw and cut it off at the metal band. You can save the wire mesh if needed and braze it back on the end cap. This will get rid of the &quot;core&quot; of the arrestor.
Using a wire feed, weld the two halves back together and grind the weld smooth w/ a flexible gring wheel. Paint w/ high heat black and put it back on. Mine took me about 1.5 hrs. start to finish. You'll also want to grind down the welds in the header. Pull the header off and look into the tubing. You'll see that the welds in the header choke down the I.D. of the tubing. Use a stone and grind them down to the same size as the tubing Add a uni-filter, cut the front part of the snorkle off(under the tank) to open up the hole bigger, add 6 uni 1&quot; vents to the airbox and go to a 152/155 main and you'll be happily impressed. Total cost of around $35.00. When you go out and run w/ or very close to the guys who have $500 to a $1000 in parts on their EXs you'll really annoy them. I know, because I do it all the time.
_________________
Keep Dunin'