50hp 400ex

[SHIFTx450]

Ok.. I'm hoping this will light up like fire. What kind of stuff do I gotta do to get my 400 up to par with the 450 motor wise? Just bought the wife an 02 400ex, I own a 06 450r. I am tearing down the 400 and building it ground up, and want the motor to rip. I know someone in here has one that's in that horsepower range. Let me know!

[Ruby Soho]

good luck hitting 50hp.

youll be lucky with mid 40's

[rob_990]

your gonna have to stroke it if you wanna beat the 450s

[dalejiw25]

Should a bought er a 450....helluva lot easier and cheaper.

[SHIFTx450]

I gotta 450. I like the 400ex though, just got the wifey one, and it's tired. Was just wondering what kinda setups you guys are all running and which is the baddest. Mid 40's i'd be happy with. I just wanna sick reliable 400ex for her to ride with me on my 450.

[rob_990]

an 11:1 416 would be easiest if u wanna run pump gas.i raced a yfz450r a few days ago and i could keep up with him till fourth gear then he pulled away

[SHIFTx450]

what other mods do you have? cam? The bike supposedly has a 416 kit in it, that's waht i was told, but i've had 2 400's in the past and i think not.. Either that or it's just tired. Smokes a bit at first start up so maybe just needs a freshening up. i fully intend on running race gas in it fyi.

[thebig450es]

Well lol, most expensive would be a turbo, but that should get you 50hp.
But then a good bore and stroker combo would prob. be the best way to get that number.
Always can run nitrous, but id say keep that for the drag

You don't mind running race gas eh?

Well then,

I would go for:

426 Bore
13.1:1 Compression Piston
Aggressive Web Cam
Hardened Rockers/Guides/Springs
Aggressive Porting
+1mm Kibblewhite Valves
Bigger Carb (450R, etc)
GT Thunder HD Headstuds
Large-Capacity Oil Cooler
Spal 4" Fan w/ Temperature Switch

That will make for one hell of a motor, that hopefully won't run too hot with the extra cooling. I don't know how much compression the stock crank is good for though..

[Wheelie]

My setup is nearly dead even with my buddies 07ER with full exhaust, filter, no lid, cam and 12 tooth. Top speed is nearly identical, and accelerating to it from a dead stop the ER has about a bike length on me. This was in the sand, both machines running 20-10-10 8 paddle extreme haulers.

This is the 4th year on this setup, no issues. I figure it makes about 44-45hp to the tires.

[hypersnyper6947]

My set up makes 37hp to the wheels, i am happy with that for sure. I think thats pretty on par with the stock 450s

[drew416ex]

Mine made 46hp at the wheels and I burn 450s all day long. There is someone on here with a 502 stroker that made around 52hp.

[thebig450es]

Not to be rude but may i ask how much it is costing to get 45+HP out of a 400ex? $2000+

[SHIFTx450]

Originally posted by DMC-4OOEX
You don't mind running race gas eh?

Well then,

I would go for:

426 Bore
13.1:1 Compression Piston
Aggressive Web Cam
Hardened Rockers/Guides/Springs
Aggressive Porting
+1mm Kibblewhite Valves
Bigger Carb (450R, etc)
GT Thunder HD Headstuds
Large-Capacity Oil Cooler
Spal 4" Fan w/ Temperature Switch

That will make for one hell of a motor, that hopefully won't run too hot with the extra cooling. I don't know how much compression the stock crank is good for though..



.. i like it

The key to horsepower on a 4-stroke is compression and cam. 450's can run much higher compression because of the liquid cooling, and some pro race 450's run anywhere from 14.1:1 to 15.1:1.
The 400ex starts to have a little heat issues at 12.5:1, and 13.1:1 is the highest I would go. That's why you would have to go with high-octane race fuel and all the cooling mods you can find, and you'll have a solid engine.

I've seen people with 12.5:1 compression and mild cams and such reach the upper 30's, around 36-38, just because of the extra compression.

So go real high compression, with porting and an aggressive cam with valvetrain that can handle it, and you should have yourself in the mid 40's with the 426 bore.

[drew416ex]

Originally posted by thebig450es
Not to be rude but may i ask how much it is costing to get 45+HP out of a 400ex? $2000+

It cost me $2000-$2500. Thats for crank, piston, cam, carb, pipe, filter, and ported head. The two most expensive things were the carb and pipe.

[Wheelie]

Originally posted by drew416ex
It cost me $2000-$2500. Thats for crank, piston, cam, carb, pipe, filter, and ported head. The two most expensive things were the carb and pipe.

Same here. Including pipe, carb, whole nine yards, about 2k. I did all the teardown and assembly myself.

[brian76708]

IMO do a hybrid cheaper faster and more reliable. i would go for a yz426 personally with a few upgrades.

[nakomis0]

The setup in my signature was dyno'd at 43hp.

As far as cost, on average 4 strokes cost $100 a HP. (if you do the work yourself.)

[SHIFTx450]

Originally posted by Wheelie
Same here. Including pipe, carb, whole nine yards, about 2k. I did all the teardown and assembly myself.

how's that E85 run?

[Wheelie]

Originally posted by SHIFTx450
how's that E85 run?

I love it. 2.07 a gal for 105 octane, a much cheaper alternative than race gas. The quad runs cooler, the oil stays cleaner, longer and it makes more power.

The only downfall is a tank of fuel doesn't last very long with the 240 main jet. This thing drinks the fuel.

Originally posted by Wheelie
I love it. 2.07 a gal for 105 octane, a much cheaper alternative than race gas. The quad runs cooler, the oil stays cleaner, longer and it makes more power.

The only downfall is a tank of fuel doesn't last very long with the 240 main jet. This thing drinks the fuel.

lol, I feel your pain. My banshee has 270's in each carb which equals out to 540 jet worth of fuel every time I hit WOT.:eek2:

[2001400exer]

i would run a big bore...go with a 465 from duncan..you dont need there cylinder just get the sleeve and have it installed in your jug...4stroketech.net should be about to get you the sleeve as i know they have them because they have a 465 bore kit that they offer...but there piston is junk buy the piston from duncan...

now its only 12:1 which when combined with a big cam compression will drop i suggest milling the head and trying to get the compression up alittle higher...high compression pistons does not mean race fuel...it comes down to cam timing this will determan how much octane is really needed...

i would run the biggest web cam if you want high horsepower and if you want good horsepower but more torque run the megacycle X6 cam...also go with the cutris sparks exhaust system

as far as carb for a 465 i would run a 41mm fcr...

also the head will need to be ported and larger valves installed..

this when done right WILL make over 50 hp

[2001400exer]

i would run a big bore...go with a 465 from duncan..you dont need there cylinder just get the sleeve and have it installed in your jug...4stroketech.net should be about to get you the sleeve as i know they have them because they have a 465 bore kit that they offer...but there piston is junk buy the piston from duncan...

now its only 12:1 which when combined with a big cam compression will drop i suggest milling the head and trying to get the compression up alittle higher...high compression pistons does not mean race fuel...it comes down to cam timing this will determan how much octane is really needed...

i would run the biggest web cam if you want high horsepower and if you want good horsepower but more torque run the megacycle X6 cam...also go with the cutris sparks exhaust system

as far as carb for a 465 i would run a 41mm fcr...

also the head will need to be ported and larger valves installed..

this when done right WILL make over 50 hp

[SHIFTx450]

Why does Curtis Sparks not recommend their advance key with high compression?

[thebig450es]

It would cause more heat

[2001400exer]

not so much the heat...but teh fact that you may get spark knock...high compression pistons will already help burn the air/fuel mix faster...so it takes LESS time to burn the mixture...well if the ignition is advanced then you are giving the motor even more time to burn the mix...but the motor doesnt need all this time to burn the mix...so the force created from the burn actualy wants to start pushing the piston in a backwards rotation...and cylinder pressure will rise to far and you can get knock...and loss of power....but yes heat will be a bi-product...