my friend has a z400 with a white bros. e-series pipe. what will it take to make a 400ex to outrun him? also he said he has beat a piped 400ex quite easily.

 

Your friend probably out ran a 400EX but I wouldn't go as far as saying "easily". Though the Z may be a little faster, these two are very close in performance and most of the time its the better rider who wins.
I would start with a good slip on and air filter with the lid removed. Properly jetted, it should have no problems at least hanging with him. Even at that, you won't beat him all the time. If you truely have to beat him you can go big bore, cam, cdi, header, etc. but just hope he don't do the same cause Zs respond better to mods.

 

I have both, and they each have identical mods. The Z is WAY faster. I notice you sig says "soon getting a 400EX". That's great if you are exclusively a tight trail rider. Other wise, I would get the Z. You will have to pour so much into the EX to even get close to that fantastic Z engine, that it just isn't worth the trouble.

 

Here's my 2 cents. I have a 400EX...W/B CDI, pipe, KN, hot cam, and the air lid removed. I can beat my friend's Z off the line without even trying...but once we get into high gear he can pass me....now he doesn't blow right by me, but he does out run me. However in the trail, I can beat him, but I have some other.."non-engine" mods that help me in the trails.

 

I would recomend a race kit.

 

i would say get a full pipe jet and filter and if that doesn't beat him slap a big ol' hot cam in there and you should be able to take him if that doesn't work high compession piston and a set of 22 inch tires if your that desparate to beat him

 

complete exhaust, k&n jet kit and filter...that will keep up with him, or even beat him by a little

 

Send the engine to 4stroke tech, and it will be smoken. I ran into a guy who had a 400ex bored and stroked to a 500cc. That thing was fast!!! Was smoken everything that was out there, including piped 450's.

 

about a year ago i only had an fmf header and silencer and a k&n wit a jet kit and my buddie had a z400 with a complete yosh system and intake and jet kit and i would get him off the line but after 2nd gear he would pass me not fly by but slowly pass and after about half a mile he was about 5 or 6 quad lenghts in front of me. after that i put a 440 bore kit in and i had no problem with being faster, you might even be able to be faster with a stage 2 hot cam.

 

i have a stage 1 hotcam forsale if your interested. the stage 2 will make you loose low end power, especially with a stock piston. pm me if your interested.