Its just tight because its on a taper,you need a puller for it which screws in the centre of the flywheel they cost about £10 from a good bike shop dont try putting things i.e screwdrivers behind it to get it off you will just damage it or break the windings on the stator coils behind it,leave a reply if you need a puller i can get you one as i work in a bike shop ok adam
adam bike doctor
March 2006