This is something Ive not tried before. The bike is a XVS Dragstar 125. 
 
Do i need to undo the allen bolt holding the internals together, thats under the bottom of the fork ? 
 
Or can I........... 
 
Take out the fork. Undo the top, remove the spring. Then after draining oil, but the fork bottom in a vice and remove the seal by pulling/pumping (hard) the top stanchion ? 
 
Any information would be appreciated. :-)