I picked up a 400ex bike about 6 months ago for 2100 bucks an 02 with tcs shocks and a white bros full pipe. I was going to use it as a camp bike that anyone could take out because it is so easy to ride and seemed to be alright on power. I took it to sand mountain and i ended up riding it because it was so under powered no one else could even get it up the hill. So the mod list started I pulled it down and had a je 11:1 440 piston and sleave put in alone with biger valves in the head and a hot cam stage 2 with new springs and what not in the head. No porting although, I think i should have now because its just not as great as i thought it would have been. I put a lectron/fast by gast 41mm carb on it has the normal K&N and all of that good stuff. I run 110 in it because thats all i run in my banshee so its there and the junky 4 stroke needs all it can get. It has the omf air scoops along with a larger oil cooler and a bigger oil tank because it just seems like the more oil you have and the cooler it is the better it will be. Oh yeah it has a cdi on it too white bros i think. The bike just doesn't seem to have the power that i would like to see out of it though. I dumped about 1500 buck into this bike so my 2100 dollar 400ex turned into a 440 ex bike that should be a beast right?? WRONG!! The money would have been more well spent on hop up for my banshee, but i have done all of this so who should i have port it or what should i do next?? I think I now realize why i hate 4 strokes so much although, there are a few 4 strokes twice the size of my banshee that will beat it.

 

maybee ur carb just sucks, get a EdleBrock carb and get it dyno tuned

 

I'm sure the edelbrock would help a lot. . but I imagine a good port job would help also. . My buddy did all that to his and his was a huge difference. . still not as fast as stock 450's though I dont think. . but very close. . I don't know. .I hate to tell ya but the 400ex just isnt a very quick bike to start with these days. . good luck though!!

 

i wish people would no comment on things they dont know about. The lectron carb is a very good carb there are a lot of racers that use them they run very well on just about anything they are put on!!!! Its not my carb! I guess its just the junky 400 oh well I guess I will just stop where im at, and call it good.

 

Ha. . .thats funny. . go back to 1999 and the 400 ex was a fast bike. . now its not (compared to everything else out). . plain and simple. . you can definitely make it faster. . but everyone's idea of fast is different. depends on how fast you want to go. Good luck with whatever u do!!

 

If you are using 110 octane fuel in a 11:1 motor you are losing a LOT of performance just from that.You could do a search on this forum to look into the technical aspects of what i am saying but pump premium is all you should need with that motor and compression.Another very critical factor in getting the most from your ex is to get the jetting as close as possible to get the most out of that carb that you invested in.I think you will be surprised to see just how much you will gain from using the pump premium instead of the 110 it is a huge difference.