Hi every one I am new to this site, what a great place- I just came off an XR400 now I have a 2000 WR400FM- It looks like from what I read, that I made the right choice for my type of ridding. The problem I am having may be normal. which is ok . When the throttle is wide open(motor not running)and the accelerator pump (AP) lever that is on the throttle shaft cam at the top of the slide travel it gos onto the flat part of AP cam which causes a notchy felling @ WOT- I checked to see if the throttle shaft or AP lever are advailable they are not. Need to buy complete carb to get these parts, from what I could find out. I hope I am wrong. Thanks very much for reading and all the really good info. Denisk--PS the throttle and AP lever look a little worn.-this may cause this problem.