I'm interested in the 4ooEX and there are some things I would like to know about it. First, I would like to know the top speed stock. Next, if I were to put an exahst system, k&n, jet kit, and a few hols drilled in the air box, what would a ball-park estimate top speed be then?

 

Why does speed matter? Top speed on a stock 400 is like 65 on pavment i think. Probably gain 2mph wit those mods. I may bewrong i may be right. who knows.

 

according to DW's mag. the 400ex's top speed is 68..yea....you might break at 70 w/ those mods....you could upgrade to a 416 and have a better top end

 

I have a FMF Powercore IV pipe, K and N filter with a dyno-jet jet kit. I also drilled a couple of holes in my air box. As for an increase in mph, I don't think that there is much of a difference compared to a stock 400ex. If there is then yeah, its probably only 1 or 2 mph more than a stock 400ex. However the mods that I have done to my 400ex gives it way better acceleration, torgue, and of course horsepower. I can pull away from stock 400ex's by a good 3-4 quad lengths and they can't catch me. So I honestly don't think that it is a major top speed increase, its just much better acceleration, torgue, and horsepower.

As for the top speed of a stock 400ex. I agree, Dirt Wheels Magazine says that a stock 400ex runs a top speed of 68mph.

Fourtracker14

 

You can't beleave DW, in the Feb, issue it says 65. I doubt it goes 70 with a pipe and flter.

 

If you want to figure the top speed just use this and fill in the numbers:

http://home.earthlink.net/~gellett/400ex.htm

 

I had my speed on my stock 400ex measured today and he said max 70. I also had a 93kxf 250 next to me and he could only do 60. I was suprised about that. He had a fmf exhaust and he said he needed a jet because it was running lean.

 

WOW, A <u>93</u> KXF250, unbeleivable. Your friend has a 1993 Tecate-4? I'm just messing with you, did you mean KX250? or KSF 250(mojave)?