To undo the allen screw (if that is what it is) you will of course need the right tool so that is the first step.
Next heat up the nut area with a heat gun since it is likely some thread lock was used.
If after removing the nut the disc will still not come off DON'T go at it cack handed with gash screwdrivers! Fabricate a puller from pieces of steel and some M6 studding and nuts.
Now, of course moving surfaces need lubrication but oil is D.E.A.T.H to friction surfaces like belts, pulleys and brakes!
Dave.
Next heat up the nut area with a heat gun since it is likely some thread lock was used.
If after removing the nut the disc will still not come off DON'T go at it cack handed with gash screwdrivers! Fabricate a puller from pieces of steel and some M6 studding and nuts.
Now, of course moving surfaces need lubrication but oil is D.E.A.T.H to friction surfaces like belts, pulleys and brakes!
Dave.