The weak point of any piston pump — automobile, motorcycle or Bicycle, as is well known, piston, or rather, leather cuff, and the main fault is a loose fit it to the cylinder walls. The fact that the skin shrinks, warps, cracks.
The case may help washer star-shaped cut from an elastic foil or plastic. The dimensions of the washer are determined by the diameter of the cylinder of the pump and the height of the piston. The part is placed under the nut of the piston, the petals of the pressed ribs cuffs to the walls of the cylinder. As the experience of operation of the pump with such a washer, the cuff works great the wear, while maintaining the pump output constant.
S. JAKAB, Lvovskaya oblast