I bought a 01 400EX from a guy a fue months ago with some mods already done to it. It has a STD. bore 11:1 piston, stage 1 hotcam, ported head, CDI box, filter, and exhaust.

The thing has a ton of low end but not the top end I was hopeing for. I like to drag race sometimes but I'm tired of getting sand im my face. I really just want to be able to keep up.

I orderd a stage 2 hotcam today. Am I going to loose to much botom end without a larger bore? What kind of power should I make with this setup? (wanting 38-40hp) Also he has a 170 main in it, does that sound to big?

Thank's for the help.

 

You WILL need heavy duty springs with the stage 2. . .you will loose a little bottom end
170?? Hows the plug?

 

call some of the performance shops they can give you a good idea of the power output.

 

you won't get that much power out of your mods. yes, definately drop the mainjet down. i would try a 160 or so depending on your elevation and temperature. what is your tire sizes and gearing? is your throttle cable adjusted properly??

 

It has a 14 and I think 38,20'' tires In the sand I was on 21'' paddles. On pavement I am dead even with a piped and jetted z400. In the sand with the paddles I can always get a good jump but get run down by 2-300 feet.

I know people are getting 40-42 hp with 416's and 426's. I'm just wondering if I can get close to the same results with my Std. bore Hi comp piston. If not I'll change it.

I'll check the cable, didn't think of that. From what I've read the stock springs should be ok.

 

i am running the stock springs with the stage 2 along with many others. yes, it is recommended to change. i have a feeling a good port job and carb will help out. i don't know how much gain you will get out of larger piston if you just want to run pump fuel. i have a feeling the people that are pushing those #'s with the 416's and 426's have more than a simple 10.8:1 piston, cam, pipe, jetting, etc. i think they will need some port work for sure and maybe even a few other minor mods.

also, my stage 2 isn't the best on the stock rev box. it revs well past the stock limit. my friends bike with a stage 1 will rev past the limit a tad too, but not like mine.

yes, check the throttle cable. adjust it so it has 1/8 to 1/4 inch slack in the lever. you adjust it right where the cable goes into the housing on the handlebars. if this isn't adjusted, your looseing a ton of power.

i would change your gearing back to 15/38 unless you only drag 300ft. we notice a very large difference when doing this on our bikes.

 

The head is ported (don't know who did it), and I have a WB rev box. The carb is stock. I was thinking of either porting it myself or sending it out.

Do they recomend shinging springs because of binding or valve float?

Whould being to rich cause me to loose topend power?

 

yes on the being to rich question, sounds like a call to pam at powroll would help you they have dyno test for almost all kinds of 400 ex set ups

 

oh, heck yeah. rich jetting can hurt your top end power.

 

the problem is you can never buy a quad that isnt stock you need to get to know it for a while before you start to change it its the number 1 unwritten rule and if you put a yamalaris sticker on it that will help mid to top end