lever blade of, undo the screw above the hosing entrance to the lever and poke something like a spoke through the hole and should pop out, may be abit stiff but will come out.
EDIT well that was for hs11 in guessing its the same with hs33 never taken one apart before,
yeah i also had this problem, i sanded it down a little and then covered it in silicone crease, worked fine for like 1 mouth then the piston leaked.