I talked to a guy today who has a 2000 400ex and he said the reason every one is having trouble with the early models of the 99 400ex smoking. the head design was messed up he didn't specify beut he said the 2000 had a redesignned head which made the performance a little better which proves my suspsion true!!!!!!!!

 

I have heard no such thing.... The head of the 400EX is the same as that used on the XR400 which as far as I know has remained unchanged since '96.

Besides, the only thing in the head that could leak is the valve guides and seals. When that is a problem it manifests itself during cold start, not when the engine is hot and has been running a while....

Sounds like your friend got some bad info....