Sledge hammer and a socket. When I actually build it, I'll use a press. It comes out the back...so pressed from the inside out. Anyone feel free to chime in...but after seeing how this assembly is arranged, I believe that variances of depth and angle of how the actual rotor head is pressed in account for the variances of power output between pumps. Even a very slight difference in depth would directly affect the pump's rack travel. Explains why some pumps run away while others can have the full fuel screw bottomed and still not get max fuel.