What are some ways to make a 400ex go faster?
Like better pistons or what?

 

Exhaust, filter, re-jet. If that's not enough save up for a 450. You won't be satisfied with less.

 

One way to make it go faster is gearing. You should be able to pick up some mph. I think an 400EX should do 60 or a little more. So maybe you can pick up 5mph with gearing - but you loose acceleration where IMO the fun is on a machine like that.

Now if you want to really make it go fast there is always.........



(Of course this will only work once)