Originally Posted by Beelzebutt

drill a hole through the center of post,, run a steel rod of somekind through the hole and use two hands to twist it out,, maybe even a cheater bar.. obviously less riskey with a steel post but it can be done on an aluminum one aswell,, you just have to do it carefully as to not destroy it.. this is all assuming youve already tried clamping a seat on and twisting it.