Suggestions for stronger 400EX

[400EX29621]

Anyone got any recommendations for building a stronger 400EX?
So far I have done the following:
HMF Slip on
Modified stock head pipe
K&N filter and airbox lid
450R front shocks
K&N Jet kit

I have been thinking adding a hotter cam and increasing the cylinder size (416,426,440???any recommendations). I have heard these kits are harsh on the engine and can really reduce reliability.

Most of my friends have upgraded to 450's. I have ridden both but dont really like either. The YFZ seat is like a piece of plywood and handles like crap a high speeds. The TRX is comfortable but feels like its tipping over in the corners, and kickstart?????

I am not giving up on the 400's just yet.

[sweet300ex]

id go with a nicely built 416 kit, a good agressive cam, some porting, and you should be havin some more fun

[prepracing]

you can look at 90% of the post on this site and see all the arguements and recomendations on whats the best build for your 400ex. I would agree with sweet300ex on this one, a nicely built 416 will do really well and is not to expensive. Then if you want to go any farther with motor mods going from the 416 on up to whatever size is no problem. If its possible I would try to find a few people with different mods done to their 400's, ride them and see which you like the best. And compare $$$ versus performance.

[2004exrider]

sounds like your off to a good start! i would go with a different cam preferably a hot cams stage 1. it is good for stock bore up to 416 piston. i'd go with a 11:1 416 piston (so you can run pump gas) i have heard they are really reliable, and ive also heard of a 440 lasting 4 years and still runnin strong. its all about maintenance. but a lot of people also say a well built 416 will keep up with a 440.

[TCracin440ex]

not trying to come off like a prick or anything...but no matter what you do to that 400 you proally wont make it beat a decently modded yfz or 450r unless the rider flat out sucks...or unless you ahve a big *** bore with alot of money in your motor

my advice would proally be 426ex kit all the way...forget the 416....fcr 39mm carb, ported and polished, aftermarket air filter, an agressive cam...maybe sparks...a good exhaust...crf 450 timming chain...aftermarket cdi...maybe some titanium valves, valve springs and retainers, and that should put you right up there...


or you could just scratch all that and do a crf 450/400ex hybrid...and still have the 400ex geometry with the comfy 400ex seat, and 400ex handling with a more powerful motor

[TCracin440ex]

oh yea...just to throw this out there too...you can have all the motor in the world but if you cant handle wortah damn...what good is it....maybe some plus 2 a-arms, axle, and get those 450r shocks revalved that should make you handle better...because it looks to me like your into mx so the arms, axle, and shock revalve or new shocks will do you great....

[bakeen]

Work on suspension and handling first. Like the poster above said you can have all the motor in the world but it won't matter if you can't keep the power on the ground. But I disagree where he said you can never keep up with the 450's. After some modifications to the engine and suspension it will just come down to rider skill. There is a point of diminishing returns with power and you hit that around the 350-450cc range (thats why you won't find any 400EX, 450R or YZF450 rider afraid of a Raptor or DS650 on a MX track). Get some +2 or +3 A-Arms. I went with Elka's instead of the 450R shocks because the 450R shocks are only adjustable 400EX shocks with rezzies. Really not very good but better than stock 400EX shocks. I have a stock engine in my 400EX but I haven't had any problem keeping up and passing 450R's unless they have better than the stock suspension. They will pull ahead in certain areas of the track but I make up for it in other areas. I'm planning on going with either a 426 or 440 myself. But I haven't ruled out the 416 either. It all depends on how much money I can put into it and what kind of quality I can get for the money. You should keep quality as top priority and not going for the biggest bore and compromising quality. MX isn't a game of he who has the most power wins (I know this goes against what all the 12 year olds on this site think but its the truth). Its 90% rider skill and 10% bike.

[TCracin440ex]

if you do the same amount of suspension mods to a 450r and a 400ex...and the rider on the 450 aint a pu$$y then all odds are in favor of the 450r walking on top of the 400ex on the mx track


440ex kit is a nice kit to have....but you will need a hd head stud stud kit because it will blow headgaskets...

[bakeen]

The stock suspension on a 450R has better shocks than the 400EX and those shocks are only a little better. Also the stock 450R is only .5 inches wider overall. Thats nothing. Other than those two things the suspension is the same performancewise. If you were to add better shocks to a 400EX and +2 or +3 arms on a 400EX then the 400EX will have better suspension which will allow you to get around a track much easier. I know this first hand. Check your facts dude.

[vinson581]

i added +2 arms, and it flat out amazed me in the handleing department, i can fly over whoops in 4th pinned, with the stocker shocks ( a little hairy sometimes) i agree a 416 with a nice port job will produce a hefty amount of power, and power isnt everything, my friend has a ds650 and its a beast yea, but isnt good in the track end of it, another guy i rode with had a raptor, and i beat him around a loop just because my bike flat out, out handled him. i cant wait till i get my shocks for how much better it will be. but the comfort, and stability factor increased 1000 percent over stock!

same goes for my friend with a widened warrior with shocks.

he can beat stock 400s in the whoops, because the bike is wide, stable, and the ride is so plush, the only thing done to his motor is a 10.25:1 wiseco .040 over, and a hotcam. power isnt everythiing SUSPENSION IS!

v581

[MerrellR89]

5 inches definately would make a difference... what are you talkin about?




Originally posted by bakeen
The stock suspension on a 450R has better shocks than the 400EX and those shocks are only a little better. Also the stock 450R is only .5 inches wider overall. Thats nothing. Other than those two things the suspension is the same performancewise. If you were to add better shocks to a 400EX and +2 or +3 arms on a 400EX then the 400EX will have better suspension which will allow you to get around a track much easier. I know this first hand. Check your facts dude.

[vinson581]

he said .5 inches or one half on an inch!

[bullwinkel]

a stage 1 hot cam and a 11 to 1 piston is all you need for power you dont need all that power in the woods.suspension.

[TCracin440ex]

ok im not sayin a stock 450r vs an aftermarket 400ex because in the handling department the 400ex will win...you do the same amount of suspension mods to a 400ex and a 450r the 450r will walk all over the 400ex in every aspect...so you get your facts straight...

[bakeen]

Its obvious theres some things you just don't get so I probably shouldn't waste my time but in the hopes of finding some inteligence I will. Put aftermarket suspension on both the 400EX and 450R and suspension wise they will be equal. Then the only thing the 450R has over the 400EX would be the possiblity of even more engine mods to maybe a 500cc or more where you really can't reasonably take a 400EX's engine. This is where the diminishing returns on power come into play. Put as big of an engine in it as you wan't but there comes a time where all your doing is spinning tires and even possibly making the thing harder to ride. Does this make sense to you or is all hope lost?

[TCracin440ex]

i get what your saying...im not talking about boring the 450r over im talking about leaving it within the 450cc limit...if you put dollar for dollar the same amount of money in a 450r and a 400ex then the 450 is still on top....if the 2 riders are the same...me myself i wouldnt touch the stock bore on the 450r....maybe a piston, cam, and some port work along with exhaust, filter and rejett....

call me an idiot but i still think the 450 has the winning ticket here no matter whats done to the 400ex unless the 450r is stock and 400ex is after market...catch my drif

[bakeen]

I see what your saying but really once you put new shocks, arms, pipe, and some quality engine work onto a 400EX your going to have a bike that should be able to take any stock 450R and even be right up there with modified 450R's in MX. Drag racing I'd pick the a stock 450R over any 400EX unless the 400EX has a real good 440 or 465 done on it (and I mean everything done correctly and quality stuff). But suspension wise your going to be equal on the 2 bikes with aftermarket mods and in MX power and speed are just one small part of the whole thing. Depending on how well your engine is done you can probably be right there with a 450R engine wise. And I agree with you I wouldn't bore a 450R. The engine is liquid cooled and I personally wouldn't want to bore it because of the way its cooled. Besides you would be putting a lot of money into doing that and getting hardly any real useable power out of it.

[vinson581]

you guys are forgetting 2 key factors.

1. frame geometry
2. cg, center of gravity, the 450 motor is so small and low, but it FEELS more tipsy then the 400ex that has a seem to be lower seat height.


put the best suspension in the world on a old lakota or something, and the stock 400ex would out handle it anyday of the week.


the 400 is awesom thats why i have one, and they are also bullet proof.

[TCracin440ex]

yea...but i still believe a 450r has the upper hand on the mx track when it comes to the 2 machines....i think the 450r has that lowend grunt you need to get out of the turns faster...and a race is either won or lost in the turns....anybody can go fast in a straight line

[400EX29621]

I have been considering +2 arms, but am worried about trail riding. Will stock 450 shocks fit wider arms? Does it benefit having the wider front w/o extending the rear?

[bakeen]

Yes widing the front will benifit more than widing the rear. But if you do both thats even better.

From what I've seen the CG isn't real any different on the 2 bikes. But I only rode a 450R once and just a little so I didn't get a good feel for where it was. CG is something that you lower anyway if your going to race MX and both bikes are much more stable compared to other quads.

[jokerman_28]

i ride trails occasionally with mine and i dont have a problem with the +2s. just keep your eye on them tires when it gets tight. as for the motor, i'm really pleased with my 440 bore. the power is incrediblely smooth the whole way.

[MAD450r]

As it says both of mine are at +2. I love both dont bet me wrong, but the 400ex will out handle the 450 all day. I have yet to ride a 400ex with long travel, but my friends long travel 450r [ he has axis all around= doesn't handle as well as my 416ex with standard travel elka's.


I am looking into getting motormounts to lower the 450r engine. I hear that will make the 450 less wheelie happy. If that solves the light frontend problem. then maybe the 450r will handle close to as well as the 400's do.

[Hondarider427]

for the extra $1500 - $2000 you spend to get a 450 over a 400 you could stick in a 400 and make it just as fastand handle 10 times better than the 450s

I prefer how the 400 ts a lot better than either or the 450s anyways

[QuadJunkies]

And get a new Carb! :macho

[clutt225]

You can def go faster with suspesion than with motor. I would take my ex that has houser +2 and rpm axle over a 440 big bore and stock suspension any day. Now selling your ex and geting a 450r sounds great, its a great starting point. My self, Im in to deep on my ex to get enough for it. It would be like starting over just to get a beter engine and less suspension. So my advise is sell the ex and go 450r or get shocks and a arms and axle.
forget the motor untill you have a bike to put it in. here is a pic of mine this motor is a untouched 01 400 and the bike as a package works great in trails sand pits and tame motocross(50' and under for me)

[Plante400]

hey. what did you paint that bumper with?

haha thanks