400ex stock header mod??

[250rforlife]

ino iv been askin alot of questions. but i have googled all my questions before asking them. especially this one. but i just hear yesterday of somehow modding the stock 400ex header and gaining a decent amount of bottom end and some mid end power from a stock header. acully comparble to the powerbomb header. and i heard it makes the exhaust sound deeper? can i get a report on how to do this, and if its true?

[finsteratv]

ive also heard of this. im wondering if a re-jet is required for this for a stocker.

[honda400ex2003]

imo yes it should have a bigger main in it. at least 1 size probably 2. from a 148 stocker to a 152 would be my suggestion for just doing that. as an example of my idea. i would just go 2 sizes on what you are already running. I dont know your setup off hand.

the mod includes grinding down the welds at the beginning of the header where it connects to the head. ill see if i can find the article on it.

ask away, thats what we are here for. lol

steve

[honda400ex2003]

heres some good pics of it.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441295&highlight=grinding+header

steve

[250rforlife]

lol so just get a dremel and grind the weilds out and make that hole bigger?? lol

[honda400ex2003]

probably an air grinder or something but yeah that is the technique i suppose. lol a dremel might work out ok too if you have a decent grinder bit for it.

steve

[250rforlife]

lol ill do this soon just to see. but u think ill notice it?

[honda400ex2003]

to tell you the truth i am not really sure. some say yeah some say no i guess. I did mine when i did my 416 and such so i cant say for sure if it helped or not. i would be willing to say that it will help top end out a little bit and wont hurt anything by doing it.

edit: after seeing your mods, i would say it will help out the stage 2 for sure. def do it and let me know how it works out for you. dont forget new crush gaskets for the head when doing it.
steve

[250rforlife]

lol ok. thanks

[honda400ex2003]

see change above^^^ lol not sure if you saw it or not before i got it changed.

steve

[ish416]

I have done this with my stock header and I couldn't tell a difference.

I did however notice a difference between the stock modified header and the powerbomb. It wasn't a big difference but noticeable.