Pulley has a threaded hole in the end for pressing the pulley wheel back on. Remove the clips from the pump that hold the plastic tank on the side by prying up the locking tab and drifting them off. An extra set of hands helps there.Get a one inch bolt in the correct thread might be 3/8" or 7/16" UNC - can't remember - and thread it into the hole. That gives you something to pound on and protects the tread from damage. It's needed to refit the pulley. Support the pulley on a large vise (or bricks perhaps) with enough room for the pump to drop down. I used an air chisel with a flat round head to pound the shaft out of the pulley, but a big punch and a BFH should do the job too. You need a longer bolt, a nut and a washer or two (liberally greased) to refit the pulley.