that nut in the picture has to come off, you snapped it off but the nut is still there. You have to hold the flywheel while you take that nut off, then pull the flywheel off the cone that is on the crank. the piece you broke is called a clutch nut. i dont see it on redcats site though, maybe one of the dealers can help you out, email clermontmotorsporst.com or alllaboutfunhobbies.com