this is a panhead part .
remove the wire in the throttle side of the handlebar and replace it by a thin throttle-cable
add a "return" spring
super-clean all the internal comps of the handlebar spiral and replace the ol'grease by oil
here is a vidéo of the résult :
i know : this is a "basic" upgrade ( and it always make me laugh )
but the owner is a newbie and the original WL throttle system gives him nightmares .....