G'day. Ive just overhauled the pump on my ZXI. it wasnt difficult once i got it apart! You do need a special tool ($25 from spare parts place) to screw the prop off the shaft. Mine was stuck together pretty tight and i ended up poring penetrating oil in the centre of the prop and letting it sit for a few days as well as gently heating the prop centre a few times. I held the end of the shaft that has 2 flats on it in a vice and used 2 spanners (one for each hand) on the special tool to undo it. The rest was easy.