what is the best engin mod you can do to a 400ex for mx?

[ThorRacing37]

^ what that saids..... Like the carb, cams, piston, pipe, sroket sizes, jets, all that good stuff...

[NacsMXer]

The "best" engine mod you can do in terms of pure power increases would be a high compression piston with a nice cam to match it. This would be the most basic mod that would yield decent power increases. Of course, you know it doesn't have to stop there..:devil: