The 400EX has one of best throttles in industry. If you don't like this IMO the problem is the rider. If you think you have problem with keeping it running or lack of power then take it to dealer. All this could very well be the rider.

 

I can only speak for two seasons on my 400ex coming from MX a couple decades ago, but i'll tell you, my 400 will take me whenere I want to and when I want to get there. As recon said, it could use some mods to get to its max potential but I think it is an overall good machine.

You need to determine what you ride and modifiy the 400 to meet your needs before you try and sell it or trade it. You'll lose at least an amount that could be used to mod it to where you want it.

I'd first have the dealer check it out and be sure it's not a lemon first.