Ok as you all know i have a 250x that runs with the stock 400's and on a good shifting day beats them.. what i was wondering is what or how could i fit a 400ex engine in my bike the engine will have everything dont to it like bored ported polishesd with the crank and everything like that and im putting my 250x engine in a gocart... just to have one bad a$$ go cart well i already so how would i make this work? buy a 400ex swing arm? and stuff like that b/c my 250x swing arm doesnt bolt through the engine like the 400ex swing arm does? so any help would be greatly appreciated! or if you guys think i should put a 450 engine thats fine with me 2.. i just love the frame and everything like the feel of the 250x it proforms great on the track! to me better than the 450's just MO the 450's and 400's all sit to high for my taste so this is why im doing the build.. ThanKS