I heard somewhere that a person could take a xr600 top end and put it on a 400ex engine. Similar to the 350x top on a 250x bottom. True/false? Cost effective? Advantages/disadvantages?

Also, what if someone put an XR400 cam in a 400ex? It is supposed to be the same. Similar to putting a 250x cam in a 300ex?

 

there is no possible way put a XR600 top end on a 400. and the XR400 cam isnt much better, as it doesnt have as much torque..maybe a race cam though
Joe

 

maybe it was a 650R top end?

 

I also heard that you can put a 650r top end on a 400ex. Im not sure if this is true but i would also like to know. I would guess it would be expensive to do though.