new 400ex

[deathticle]

hello i just got an 05 400ex and im already looking for more power whats the most power i can get without going to race gas what mods would i need?

[TacicalRedneck]

What octane are you using now?

If it's not piped that should be first. Air filter... those little things..

My 2 cents.

[400exwhipper]

A slip on + filter and 93 pump gas seems to run great and make great power

[red200040ex]

You could get the above plus a cam and a higher compression piston if that still isn't enough.

[deathticle]

i want to go all out and top out the 93octane. 11:1 piston from what iv read, hmf slip on, now can i do a 440 kit is it worth it if im only on 93? hot cam?

[05DodgeDakota]

You can make whatever mods you like and stay on pump gas as long as you do not exceed 11:1 compression ratio, adjust the timing, use nitrous or turbo it. Other that that your good to go. Any size bore, any size cam, any size crank, any head work, any intake, any exhaust, any carb, etc. Race gas in itself does not add power, it simply resist knock, which comes from increased timing and increased compression.

[deathticle]

so if i go to a 440 will i need a new carb?

[deathticle]

so if i go to a 440 will i need a new carb?

[300exBorg]

450R carb with that would be nice

[CJM]

Originally posted by deathticle
so if i go to a 440 will i need a new carb?

No, but you would be smart to install one.

Please take into consideration the following build:
11:1 86mm piston.
stage 2 hotcam
good exhaust
04-05 honda 450r carb
open air box

That will build you quite a fast 400ex. A 440 is nice but once you wear out the bore your SOL-gotta resleeve.

[deathticle]

i cant get any bores off a 440 at all? how many hours will one bore last?

[CJM]

Originally posted by deathticle
i cant get any bores off a 440 at all? how many hours will one bore last?

A 440 cannot be bored out again, you need to resleeve it. You actually need to buy a new sleeve to do the 440-it cant be bored to that size. How long it will last, thats up to you-more you ride the more it wears. I ride an avg of at least 250 hours or more a year and usually get maybe 2 years out of my setup.


Many have ran that same setup I explained earlier and have been VERY happy.

Bore size does not equal power, compression is power.

[deathticle]

so a 440 11:1 will make the same as stock 11:1?

[Drfat400ex]

Originally posted by deathticle
so a 440 11:1 will make the same as stock 11:1?
Well you should get a bit more power with a 440, but you'd be alot better off not to. If you don't do a big bore perfect it will over heat, jetting is really tricky on them and it has to be spot on, and even still you may end up having to put on a larger oil cooler and a spal fan. After all the trouble, in most cases a 440 isn't worth it.

[05DodgeDakota]

no replacement for displacement ring any bells? All other things remaining equal, a 440 will make more power than a 416. Power may come on differently so to speak, because a smaller, lighter piston and shorter stroke normally will be able to rev faster, but a bigger displacement motor should make more power. Downside as stated is you have to resleeve everytime you rebuild it. You can also add stroke too if you feel like going into the bottom-end


I'll repeat it since I edited my prior post:

You can make whatever mods you like and stay on pump gas as long as you do not exceed 11:1 compression ratio, adjust the timing, use nitrous or turbo it. Other than that your good to go. Any size bore, any size cam, any size crank, any head work, any intake, any exhaust, any carb, etc.

Race gas in itself does not add power, it simply resist knock, which comes from increased timing and increased compression.

[deathticle]

Alright so I think I'll stay stock bore but I'll put a 11:1 piston and a stage 2 hot cam? Or stage 1, exhaust, intake, rejet and maybe I'll look into some port and polish work

[TheAwesomehonda]

Originally posted by deathticle
Alright so I think I'll stay stock bore but I'll put a 11:1 piston and a stage 2 hot cam? Or stage 1, exhaust, intake, rejet and maybe I'll look into some port and polish work That sounds good man but i would just go with a 416 bore. btw that ex looks nice!! Also you may want to replace your cam chain and clutch if your taking off the right crank case cover but that stuff probobly isn't worn out yet on a 05.

[05DodgeDakota]

No way to know what is the smallest size bore is that you can go with till you take it apart and measure it. Mine was so worn out I had to go to a 416. Also even if it is fine, you need to hone the cylinder before installing a new piston. Also he studs and the crf cam chain are cheap insurance.

[dxcody]

Originally posted by TheAwesomehonda
that stuff probobly isn't worn out yet on a 05.

You gotta think dude, an 2005 is 7-8 years old.

[TheAwesomehonda]

Originally posted by dxcody
You gotta think dude, an 2005 is 7-8 years old. Dude just think about it!! Th clutch and cam chain aren't effected by age there effected by the amount and type of riding. If a ex has less then 200 hours the clutch and cam chain are probobly still good. It just depends on how much it was used..

[deathticle]

i put 10hours on it from when i got it and i would say i could not have had more than 15 when i got it so maybe 25
total

[TheAwesomehonda]

Originally posted by deathticle
i put 10hours on it from when i got it and i would say i could not have had more than 15 when i got it so maybe 25
total That is really low hours but remember you would put that much on with 2 week ends of trail riding.. It looks like its low hours b/c the paint is still on the crank case by the foot. If those tires on there replaced the worn out stock ones then it has more then 75 hours..

[CJM]

Originally posted by TheAwesomehonda
Dude just think about it!! Th clutch and cam chain aren't effected by age there effected by the amount and type of riding. If a ex has less then 200 hours the clutch and cam chain are probobly still good. It just depends on how much it was used..

maybe or maybe not. Friend of mine bought a pretty mint looking 05 EX, the paint was not worn off the frame to much and it looked to have been ridden maybe 50 hours.

His cam tensioner snapped and left us on the trail 10 mins after we got there after he had only put on maybe 10 hours himself. Chain, tensioner, guides, etc all were no good. As was the topend someone tried to repair. Maybe he got a lemon, but you never know.

[deathticle]

so i should do the crf cam chain just to be safe?

[CJM]

Originally posted by deathticle
so i should do the crf cam chain just to be safe?

Its a matter of piece of mind. Your going to have almost everything apart anyways so its worth the extra few bucks to replace the chain and cam tensioner if they are bad as well as the guides if they show wear.

[TheAwesomehonda]

Originally posted by deathticle
so i should do the crf cam chain just to be safe? Yeah and if you do that measure the clutch triction plates to be sure there still good.

[deathticle]

about what hp would i be at with a 416, 11:1, stage 2 hot cam, hmf slip-on, k&n?

[dxcody]

Originally posted by deathticle
about what hp would i be at with a 416, 11:1, stage 2 hot cam, hmf slip-on, k&n?

I wanna say around low- mid 30's maybe 33-35 HP

But idk. Just a guess.

[Ruby Soho]

its all on the owner.

i had a 99 400. had a 440 in it, put more than 250+ hours on it. never once overheated on me. stock clutch, bottom end you name it. i had the wiseco 89mm i think it was piston, bored sleeve, gt thunder hd studs, the mls head gasket, decked head, stage 3 hotcam, 450r carb and a whitebros mx4. all that i can remember off the top of my head. i beat the **** out of that quad, but took care of it.