HI,
The clutch centre has an internal thread for an extractor, be careful as there are two different threads on the available pullers
You should need the 26 tpi one, make sure its threaded fully into the centre before tightening the centre bolt
Some heat from a heat gun will help, tighten the extractor bolt, apply the heat and if necessary a firm thump with a copper mallet on the bolt head will remove the centre
A problem can arise with primary chain alignment when a new centre is fitted, due to different taper depths
Also lots of poor quality centres out there
A thread file should clean up the shaft, If I cam remember its 5/8th x 20tpi
HTH
John