I didnt mean it wont add power its just so innefective to the cost of having it done its worthless. After you buy a new piston and pay to get your cylinder machined you could have purchased a more bang for the buck part, like a camshaft, or taken the money to get some riding lessons that will make you a faster rider with the power that you already have.Change cams.
I don't see how you figure boring doesn't add power? On a 400EX, if you bore it to the max on the stock cylinder it makes it a 416cc. That is not going to be a huge gain but it wil produce more power than a 400cc.