yo u have been misinformed , a rd400 is alot different i n the fact the engine is air cooled,igniton is different, the crank uses longer 115mm rods, it also is a huge +8 millimeter stroke compared to your banshee crank ,in other words its not gonan fit with out case trenching ,your port layout on your she jugs wil l not work eve n remotely close without major modification ,your pistons wont work either nor the head unless these things are all modifed . you wil l surely need way more than yo u thought