To start, pick up the rubber. You can use regular rubber gaskets for water tap that bend easily and are quite durable, but keep in mind, they must be made of oil-resistant rubber. Otherwise, the lifespan of your seal going to be over too quickly.
Take the drill, clamp the rod, on which is placed a gasket. Turn the instrument on and, using a sharp knife work on the rubber band so that it became similar to the standard. Make the lower part with a thickness of about with the plastic washer under the piston thickness can pick up a little.
Sand the edges of the piston nulevkoy so that they become sufficiently flat and smooth. This will ensure that his good work in the future. The top wall of the piston from the inside grind to an acute angle. The outside of the piston should extend upward about the same as standard.
Ensure that the gland was tightly clamped with a plastic cover with the spring to prevent possible leaks. The hole in the middle should close-fitting aluminum piston.
If the stroke is tight, then try to disassemble the figure and pump with the use of a lubricant, the piston should begin to go effortlessly. If leaks are not found you, and stroke you are not too tight, you can leave everything as it is. But be careful: too heavy a stroke can cause damage that will entail the purchase of a new.
If you notice a leak, then most likely you will have to work with the piston. The case may be piston damage during Assembly, for example, there can be holes or bent. This piston is not suitable for further use.
If the handle moves easily enough, leaks are not observed, then congratulations with a good result. You did the right thing.