400ex build need some help

[theduke300]

im wantin to have one of the baddest 400s around i just dont no wat to go for. im alredy bout bought a 2006 400 all stock. i dont no to go with a 460 stroker kit or ive seen talk about 503 an 505 kits. i just dont no for sure. also should i go stage 2 or 3 hotcam or??? i just aint never done a big project like this an i need some help. any advice wuld be preciated

[B.C.#11TRX400EX]

Since its all stock i would go for like a 426 or 440, with Stage 3 hot cam, Sparks Exhaust, 450R carb, K&N Filter with outerwears, and Jets R Us Jetting Kit, Thats what i would do

[theduke300]

so you wuldnt stroke it? an thanks for replyin

[CJM]

GT Thunder, Sparks or CT racing will make you one hell of a stroker that will give excellent power-but be prepared to spend ALOT of money on the motor itself.

426, 11:1, 04-05 450R carb, stage 2 hotcam. This will build an ultra reliable machine. then spend the cash on the suspension. But a 400EX will still never be a 450-can it beat them-sometimes, but dont expect to have the baddest EX without spending alot of coin.

[thebig450es]

Call Laz up at GTThunder, nothin like ridding a 87mmx77mm engine

[theduke300]

well you guys got numbers for anyof these guys? and wat kinda price am i lookin at just for te bore an stroker kit

[B.C.#11TRX400EX]

from wat ive seen the more u put in the engine the less time the engine lasts, when a engine runs at really high RPM's they don't last as long and that means more money to be spent, so i would bore it as small as i could get it, then when it needs it again i would bore it bigger then keep going up, your engine in my mind would last longer that way, thats just my thinking:ermm:

[CJM]

Expect 40+ hp and to spend at least 1500 bucks (more like 2000+ tho after everythings said and done) on just the motor.

a 416 or 426 build is about 500 bucks.

[chronicsmoke]

I'd take CJM's advice, If you want a badass 400, bore the stock cylinder, port the head, hotcams, new timing chain, exhaust, and save the rest for suspension..

Or sell the 400 and buy a bigger bike for the money you plan on spending.

I do agree that bored/stroked engines are sick and probably haul the mail, but the reliability issues worry me. They require more maintanence, which IMO is the reason why the 400ex's are so popular. Reliable and fun to ride.

In my mind, a heavily modified 400ex will require the same, if not MORE, mainanence than a stock 450r. And they will have similar HP

JMO.. but then again, I dont have 2g to spend on my 400ex motor..

:blah:

[Ruby Soho]

in reality if you want that kind of power just buy a 450r. your going to put more money into the 400 that you'll never get back, then if you just sell it and buy a 450r for less.

[slightlybent47]

RPM’s is your least concern. The rev limiter will keep it from over revving so I would worry about that.
As for reliability my 416 ported, 2 cam, 450 carb has ran strong for 5 years now with no issues.
Keeping it clean with fresh oil and clean filters do more for reliability then anything else.

[chronicsmoke]

Originally posted by slightlybent47
RPM’s is your least concern. The rev limiter will keep it from over revving so I would worry about that.
As for reliability my 416 ported, 2 cam, 450 carb has ran strong for 5 years now with no issues.
Keeping it clean with fresh oil and clean filters do more for reliability then anything else.

That's what I'd do if I had to do it over from scratch.. 416CC, 11:1, Stage 2 Cam, P&P, 450r Carb.

I like my setup, (426CC, 10:1, +3Key, Stage 2 cam, P&P) , but I wish I had the option of boring up without going all the way up to a 440. (I also wish I had a spare 450r carb to add to it.. sigh:ermm: , maybe this winter after racing season is over..)

[theduke300]

alrit guys thanks. ive been lookin an i think i got a pretty good idea of wat i want. 416,stage 2 hotcam,curtis sparks full system,450r carb. outerwears an k and n filter. then put more cash in the suspension.port an polish. should i go 10:1 or 11:1 piston?

[slightlybent47]

I’d do a mild port job while you’re in there. I would only go with 11:1 or higher if I had access too race fuel and you don’t mind paying $10.00+ per gallon. Otherwise stay at 101/2:1 or lower.
And one word of advice, skip the K&N and stay with the stock foam filter. It works much better and at best with ½ Hp gain it’s not worth the risk of wrecking all that motor work you are about to do.

[theduke300]

okay so hows this sound guys.

416 cc,10:1 piston,stock air filter, mild port job,curtis sparks pipe,450r carb,stage 2 hotcam. then a good suspension.

am i missin anythin?

[chronicsmoke]

Originally posted by slightlybent47
I’d do a mild port job while you’re in there. I would only go with 11:1 or higher if I had access too race fuel and you don’t mind paying $10.00+ per gallon. Otherwise stay at 101/2:1 or lower.
And one word of advice, skip the K&N and stay with the stock foam filter. It works much better and at best with ½ Hp gain it’s not worth the risk of wrecking all that motor work you are about to do.

x2 about the P&P! you're already in there!

I'd feel comfortable running 11:1 with 93 pump gas, I wouldn't want to run 87 in it though.

Uni filters are my preferred company.. they rival K&N in popularity and performance, but are proven to trap more dirt/dust than a regular K&N. Did I mention they are half the price too?

You'll need some different jets for the carb, but that's the last of your worries right now. I would also take a hole saw and put some holes in your airbox lid for better airflow.. I would replace the timing chain too.

I'm not sure if you'll need HD studs at 11:1 compression.. wouldnt be a bad idea.. but I'll let CJM elaborate on that if he's around.

By the time you're done, you'll have a pretty strong running motor

Time to start shopping!:macho

[chronicsmoke]

Originally posted by theduke300
okay so hows this sound guys.

416 cc,10:1 piston,stock air filter, mild port job,curtis sparks pipe,450r carb,stage 2 hotcam. then a good suspension.

am i missin anythin?

I'd do a timing chain while you're in there too, it's only 50$. (CRF450 Timing chain will work, and is of better quality)

Any ideas on supension, or is that another thread for another day? lol

[slightlybent47]

I have 12.5:1 with the stock head studs and I’ve had no issues with it.
If you plan to do a lot of riding id stay with low compression. I don’t ride that much and it’s all MX so I don’t use that much fuel. If I were riding trails and did a lot of riding it would be too much money for fuel.

[theduke300]

yea i ride real often.

Yea thats actually wat i was gunna ask next haha.

what does everyone think?
shocks???
a arms???
watdo yawl think?

[chronicsmoke]

Originally posted by theduke300
yea i ride real often.

Yea thats actually wat i was gunna ask next haha.

what does everyone think?
shocks???
a arms???
watdo yawl think?

Shocks - Something that is valved for you (I'd try and find used ones in good condition, already set up for around your weight/application)
A-arms - Something in decent shape from the Classifieds section.. (I'd get anything +2+1 that use a Standard Travel shocks)

You're not racing, so even a pair of stock 450r shocks will make a difference.. for the rear, I'd get it revalved. (splurge on a GTT link if you've got the $$)

JMO

[theduke300]

whats the price range for a good set of shocks an arms

[CJM]

Originally posted by theduke300
yea i ride real often.

Yea thats actually wat i was gunna ask next haha.

what does everyone think?
shocks???
a arms???
watdo yawl think?

Good idea to do the head studs qwith the hi-comp piston, its 100 bucks of insurance (50 for the studs and 50 for install if GT Thunder does it). Not truly needed, but you just never know. What happens is the exhaust heats up quite a bit and causes the aluminum to basically get so hot the studs pull out on the exhaust side.

I think your gonna like the 416, I love mine. It lugs like a tractor if I want but also has damn near awesome power. Its no 450 but it can keep up with them fine.

As for shocks:
1. Aftermarkets if you want, be prepared to spend $$$ if you buy fox, elka, pep, etc.

2. Buy honda 450r shocks, or yamaha yfz shocks. 450r shocks will raise up the front a tad and are a bit stiff for some. you also need to slightly modify the frame to get them to fit (DO NOT GRIND THE DAMN SHOCK EYE if someone suggest it, its not a bad idea but if you go to sell them off NO one will ever want them).

Or buy the YFZ shocks. You gotta cut the top of the shock eye slimmer on these-no choice. They ride softer and lower the front about an inch.

2A. Buy either of those and get them reworked along with the stock rear shock for your weight and riding style.

2B. Look into the GT Thunder XC or MX shock linkage. It does lower the quad but eliminates all bucking you get form whoops.

Expect to spend about a 600+ on a good setup. Remember, better it handles the faster you can go with it. So speed is in direct correlation to how well it handles. A stock 400 with a good suspension will beat a modified engine 400 with stock suspension.

A-arms are a personal choice, I like JD performance myself b/c he custom builds each set for you anyway you want., houser is nice, bugard is nice, as is many others. If you dont ride to many trails +2 is good (thats +2 added in inches to each side), otherwise stock sized or +1 is the way to go for XC style riding-narrow enough to go thru the woods well but wide enough to offer better handling. The arms range from 400 for a good set to over 1000 for various other makes and models. Try and find a set that doesnt use heims, they wear out to easy, squeak if not lubed and arent sealed as well as ball joints.

If your gonna race MX Id recommend a g-force extended axle. They are sold at rocky mtn atv/mc, are rather cheap but excellent axles-quite strong. I used to run one and never had an issue-only swapped b/c I wanted less width.

Thats pretty much it in a nutshell. My personal build would be:
-406 or 416 11:1, JE, Wiseco or CP piston. Power is compression not bore size too much. also 10cc's doesnt matter that much in reality when your comparing piston sizes. Remember less size you go for-more it can be bored later if needed.
-Stage 2 hot cam
-04-05 450r carb
-good exhaust (a slip on isnt actually half bad vs a full pipe either btw, the difference is minimal)
-uni filter
-EHS outwears open air box lid kit. This is a kit you cut a hole into your airbox and sandwich the outwears material in with a bracket they supply. More air feeding the machine the better imho. Water isnt really an issue either, outwears and filter stops 99% of it unless you ride in really wet areas.
-Razr 2 fronts and razr 1 rear tires. Max= 20" fronts and 18" rear, XC or anything else id do 22" fronts and 20 or 22" rears
-Gearing can be left alone in most cases, stock 99-04 is 15/38, 05+ is 14/39 iirc. If anything with the power band you will have going down one tooth in the rear will give you a bit more speed you need. For me I could use this as I can blast thru the gears very quick-good for tight woods but bad for wide open areas.
-4" spal puller fan. This is attached to your oil cooler and pulls the heat off it. its small enough to pull substantial air without draining the battery.
-CFm or Um larger oil tank, extra cooling is worthit, tanks 100 bucks
-SKID plates! Dont skimp, buy the thickest ones you can find (.250 aka 1/4") if your gonna trail ride. If your doing MX there not really needed.
-Lastly a good battery is a must. Throw away the stocker and buy yourself a YT-16B iirc, or whatever they call a suzuki hayabusa battery. Same size as styock but almost double the power.

Thats pretty much it. The above is pretty much how I built mine and it does rip. I have plenty of power to a degree-these days it almost feels slow to me tho lol cause Im so used to it.

[slightlybent47]

You can find good used parts for the ex. I’d do a +2” in the front, (long travel if you can find one) but +2” standard travel will work well with stock 450 shocks.
Have the rear shock re valved and sprung for your weight. Or find a good used elka.
Then do a +4 on the rear axel.
That’s basically what I have and it handles 80-100 foot jumps pretty well. But it’s not top of the line and it lands very hard when I go that big. In fact I’ve snapped axels because of it.
You will lose some power by going wider but cornering is way better and worth it.
Also wider rear axel will make it spin more coming out of the corners but you can go into them so much faster that it works out better in the long run.

Used 450 front shocks in good shape $100-200 bucks.
Used +2” a arms $100-200 bucks.
Used +4 axel with hubs $200-300 bucks.
Re valve and spring rear shock $60-100 bucks.

[theduke300]

ok sounds good. couldnt think you guys enough.

[CJM]

x2 on bents advice if your going into suspension on the cheap. It will work, just might not be as totally cushy as a full on custom setup-but its damn cheaper :devil:

As for everything else, your welcome. Feel free to ask more Q if you need.

[theduke300]

alright. this builds gunna be a slow process but ill keep yawl posted on it. an be ready for tons of questions from me along the way lol

[Stickman400]

Damn CJM, that's a pretty good post summing up everything you need for a good base. I'm gunna take a couple of those ideas and use them also.:D

[CJM]

Originally posted by Stickman400
Damn CJM, that's a pretty good post summing up everything you need for a good base. I'm gunna take a couple of those ideas and use them also.:D

Your welcome.

I keep telling everyone thats the way to build it. Do it that way and its reliably, doesnt overheat, has power and makes you smile BBBRRRRAAAAAPPPP! :devil:

[chronicsmoke]

Originally posted by CJM
Your welcome.

I keep telling everyone thats the way to build it. Do it that way and its reliably, doesnt overheat, has power and makes you smile BBBRRRRAAAAAPPPP! :devil:

X2

thats like the ideal 400ex
IMO any desire for more power would be better suited with a 450.. better base to start with and more potential with liquid cooling..

[CJM]

Originally posted by chronicsmoke


thats like the ideal 400ex
IMO any desire for more power would be better suited with a 450.. better base to start with and more potential with liquid cooling..

Agreed