why is my z 400 so slow

 

Because your going from a modified DS to a Z, quite a power difference . And actully the Z's speed is respectable for a 400.

 

I think he modded his Z400 and was told to go down 3 tooths in the rear but he went down 3 tooths in the front.

 

It's slow because you were trying to go in a straight line. To go fast on one i think you need to turn alot, at least thats what the other z owners say. Or you made a mistake and rode another sport quad first , in that case your screwed and it will always seem slow. J/K

 

Do what you have done to your DS to your Z....for example...new carb (FCR 40mm), new ignition (Dyna/Vortex), new exhaust, air filter, ported intake, and then come back and say its slow.