400EX into crf450r questions

[Mattg8230]

Hey guys i gotta 99 400ex with many race modifications and Im trying decide if i would rather buy a crf450 motor and put it into my 400EX or bore my 400 Engine into a 440. How much work would it be to put a crf450 Engine into my stock frame. Any suggustions you guys can give me would be great!!

[Knips178]

do a search on crf450 conversion for a 400ex and you'll find one with a full how to section of what needs to be done. It doesn't look easy.