No way can I get the fecking thing off, it’s seized solid. Corroded to the shaft I guess. All suggestions as to how to unseize and remove it are very welcome please. The bolt head you can see between the sprocket puller central screw and the gearbox output shaft is there to prevent the sprocket puller pushing down into the central hole in the output shaft, which it was doing. TIA ps. Judicious amounts of penetrating fluid have already been applied over days to the sprocket/shaft join.