race motor

[russellsroost31]

ok guys im gonna rebuild my motor for mx how does this sound
440 wiseco or je kit at either 12:5:1 or 11:1
stage 2 hot cam
stock carb rejeted with K&N
fmf power bomb header to hmf slip on
tusk clutch plates with hd springs

[ish416]

Sounds like a good build but I would throw in some head porting, HD head studs, OEM XR400R gaskets and an 04-05 450R carb or FCR carb on it.

Also, going over 11:1 will require either E85 or race fuel, so keep that in mind.

Also, if you plan on racing against anything but stock 450's you will get raped. Badly. At least as far as power is concerned.

[dxcody]

Won't this be the 2nd rebuild you have done? Don't mean anything by that, i am just curious.

[JOHNDOE83]

I do highly recommend the 440 kit for any type of racing.

I will say that if you have some money for motor work, get the kibble +1 or +2 valves and a really good slightly agressive port job.

The valves and cam along with a good 450r carb and port job will be a big improvement over your current setup.

The 440 kit is awesome for power now needs, it also is good for using different sproket combos and tire sizes for more speed and more gear adjustability on different tracks. One track you may want 16/36 gearing and another you may want 13/39, the 440 will make all combos WAY more efficient.

Anyway, the head work in my opinion is the way to go first. This accomodates all the other mods, the bore kit alone isnt all that impressive without it. The best option is head work first, then its done, you can always add a bolt on 440 cylinder kit later.

Then youll have almost the same motor I have :devil:

I may be selling my motor soon to.

[slightlybent47]

Do a little more research first. There was a shootout in dirtwheels between the 440 and a 416 and in most cases the riders liked the 416 best overall over the 440.
Doing all that work and not using a 450 carb, wont help that much.
Head work and compression will yield the best power.
Stay as far away from a K&N filter as you can. If you have one, hold it up to a light and you’ll see little holes everywhere. Guess where the dirt will go, that’s rite, strait in your motor.
Stick with a well oiled stock foam filter. You will here lots of arguments on how well the k&n is, but its all hype, yes it flows better, but it also lets in more dirt.
You watch, there will be a bunch that will tell you otherwise.

Just remember, head work is where the power is, not displacement.

[russellsroost31]

ok
now im just running modified stock headers should those be fine and ive been running K&N for a long time now and i haven had a single problem and i ride in dust mud and all of tht fun stuff
idk y u guys have a huge problem with them i havent seen any problem whats so ever
ok ill just stick with 11:1 and the 450 carb is to come soon ive only got like a month to get this all done i can do all the work my self and yes this would be the 2nd rebuild
the first one was because of my tranny

[Stickman400]

Grinding the header welds on the stock headers would be nearly as good as having an aftermarket header, so you are good to go there. And as long as you are running an outerwear over that K&N you are fine. But if you aren't I'm amazed you haven't needed a rebuild sooner. I've seen a couple 400s with K&Ns and no outerwear that had LOTS of dust built up in the intake tube. I can't imagine what that did to piston, cylinder and the head.

[russellsroost31]

nope i dont run one
i love my K&N only filter ill ever buy great power pretty dam good protection also

[CJM]

Good luck with the KN...

[russellsroost31]

well it seems to be working for me
ok now if i just put the 440 wiseco kit with 11:1 the stage 2 hotcams grinded header welds hmf slip on stock carb rejeted and the K&N how mhuch hp ashld i be around

[DragonGunner]

Originally posted by russellsroost31
ok
now im just running modified stock headers should those be fine and ive been running K&N for a long time now and i haven had a single problem and i ride in dust mud and all of tht fun stuff
idk y u guys have a huge problem with them i havent seen any problem whats so ever
ok ill just stick with 11:1 and the 450 carb is to come soon ive only got like a month to get this all done i can do all the work my self and yes this would be the 2nd rebuild
the first one was because of my tranny


13 yrs on K&N.....No problems, over 5 yrs K&N on a KTM motor....no problems.....scores of Pro GNCC racers used K&N....Chad Duvall ran his 500EX with them......but....haters going to hate.

[russellsroost31]

amen to those results

[odog]

with that 440 kit i wouldnt even waste time with the jet kit go ahead and get an fcr carb or 450carb or you ll be holding that beast back.

[russellsroost31]

how hard is it to install a 450r carb will it take alot of modifcations or will she bolt right on in

[ish416]

04-05 carb bolts right up. FCR may or may not depending on where it came from.

[Wheelie]

X2 on the carb.

Nothing wrong with K&N filters, been running one on my quad for 11 years--never had so much as a spec of any foreign material in the intake tract.

[russellsroost31]

ok guys thank you so much for this info
what shld my jetting be around atleast 175 for the main i would think

[DragonGunner]

with your set up...open airbox on a stock carb I would start with a 180, but it depends on the temperture, if you going to run in cold winter or warmer weather. I run a 180 main needle raised one notch, but in cold weather I need to throw a lid with 8 one in. holes in it to cut back on the denser air for it to run good......easier to do that than swap out mains.

[odog]

if you get your carb from sparks it will bolt right up. if you tell them how your engine is built they will jet it for you it will be pretty close and they will also send you a couple of extra jets for it but it is expensive but the fcr carb have great throttle response over the 04-05 carb.

[russellsroost31]

i may just stick with stock to save some money
its not like its gonna b a huge major power gain it will be like wht 2 maybe 5hp at max with the 450 carb

[odog]

ok i guess in your opinion 2-5hp gain on a 400ex isnt much but for me my carb gave me more power than going from a procircut t-4 slip on to a full x-g bigcore sparks exhaust.after all the work i had done on my bike until i got that carb my bike didnt fell scary fast it does now.if i had an stock ex and was starting a build all over again the carb will be one of the first things i changed.This post says race motor ITS NOT A RACE MOTOR WITHOUT A REAL CARB.

[russellsroost31]

ok ill get one later on but i think just for now ill stick with stock

[JOHNDOE83]

Originally posted by odog
This post says race motor ITS NOT A RACE MOTOR WITHOUT A REAL CARB.

^ deffinetly

[russellsroost31]

hown bad will my reliability be with this build just out of curiosity
oh and im not even running my air box right now you guys think i should put it back on or keep it off and let her get as much air as she wants

[JOHNDOE83]

if its put together correctly with new parts and jetted properly it will be just as reliable as a stock motor.

As far as the air box goes, if your MX racing, goofing around with friends, trail riding it should be 100% ok. If your going out in wet conditions or racing after a heavy rain I would Deff put it on.

I would bring main jets that are atleast 5-10 incriments smaller just in case it stutters on the top end with the box on.

[russellsroost31]

alright thanks guys
ill just bring the airbox with me and if its really wet or somthing ill throw it on it onlyt takes like 10 mins

[DragonGunner]

Originally posted by russellsroost31
ok ill get one later on but i think just for now ill stick with stock


Chad Duvall ran Pro class GNCC for 2 yrs on a 500EX stroker, he won many races and won the pro production class.....he ran it with the stock carb. He won agaisnt 250R's and against YFZ450....so there you go.

[Longdong]

This is a very funny thread!

[russellsroost31]

whys that