400ex needs power

[shellz4sand]

I just bought a 400ex, this is my first four stroke.It is lacking in bottom end power.I took it to sand mountain this weekend & had to pull the steep hills in 2nd gear pinned.Do you think a 440 bore kit would pep it up alot?It already has white brother exhaust.I need more power.

[enduro400rider]

go with the 416 kit high comp piston from JE or Ross and a good cam. most people are goin to tell you get the 416 seems to be a pretty popular set up. search the site and you will find alot about the 416 VS 440. plus if you go with the 416 you dont have to resleeve and you have 2 more bores left good luck

[85atc350x]

A inexpensive way to gain lower end power is to drop one tooth on the front sprocket.

[huffdaddy_400EX]

I take it from your signature that you only have a white bro exhaust...no other mods?

When you went to sand mountain did you rejet? Sand mountian is about 4100ft.

I had issues with some hills but after an airbox mod (ehs racing lid) and rejet I can pull them in 3rd and some times 4th...and I'm not a small fry either

[mx400]

gearing bro. gearing is your key. drop to a 14T front.

[shellz4sand]

Originally posted by huffdaddy_400EX
I take it from your signature that you only have a white bro exhaust...no other mods?

When you went to sand mountain did you rejet? Sand mountian is about 4100ft.

I had issues with some hills but after an airbox mod (ehs racing lid) and rejet I can pull them in 3rd and some times 4th...and I'm not a small fry either

I live at 4700ft so I should be good on my jets.That airbox lid increased the power that much?Is that about the same as the K&N lid?

[shellz4sand]

Originally posted by mx400
gearing bro. gearing is your key. drop to a 14T front.

Is it easier to change the front or the back ? So a 14T will help?What is the best to change front or rear?

Originally posted by enduro400rider
go with the 416 kit high comp piston from JE or Ross and a good cam. most people are goin to tell you get the 416 seems to be a pretty popular set up. search the site and you will find alot about the 416 VS 440. plus if you go with the 416 you dont have to resleeve and you have 2 more bores left good luck

2 more bores left? LOL.. 2 more bores would make it a 440 on a stock sleeve.. and i dont got that lasting 2 minutes..

check your info bro.

Jesse

[huffdaddy_400EX]

Not sure about the K&N.

Here is a pic of the lid. It allows more airflow...and the outwear gives you more protection then running no lid at all (which is what I used to do).

[mx400]

the front is the easiest to change imo. and it is gona increase quite a bit

[huffdaddy_400EX]

I agree with mx400...dropping a tooth will show a good low end increase. My original reply was about jetting...but since you're at 4700 anyways go with the lower front...you'll like it.

[shellz4sand]

Thanks Guys, I bought a new one for the front, and I am going to get the airbox cover,change my front tires to sand tires and hope for the best!:blah:If it runs better I will put some kind of bore kit in it. If not I see a new 450 in my future.

[LazeR]

also you could try putting a HMF Slip-on or full exhaust on it.....My friend rode my quad and said it was the fastest 400ex he has ever ridden and he had one with a full WB exhaust on it....

[400sEXridr]

instead of buying that EHS Racing lid (which from i've seen was pretty expensive) you could just buy the outerwears airbox cover (about 15 bucks) and cut the center out of your stock airbox lid. that way its a lot easier to remove than the EHS one and a lot cheaper too.