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Replace the O-rings using the yellow and black tool that was designed and 3D printed for this purpose, found in the Kuster accessories box. Use the tool as follows:
A. Remove the top bracket of the tool and place the valve assembly in with the spring up(fig. 16)
fig. 16
B. Place top bracket on so that the spring fits into the center hole and screw it down until the lower limit nuts are reached. The spring is now fully depressed. Now remove the two split rings that become exposed(Fig. 17).
fig. 17
C. Unscrew and remove the top bracket completely and now you may remove the spring cap, spring, and valve from the body of the assembly(fig. 18).
D. Remove and replace the O-ring.
E. Repeat steps A-C in reverse to put together the valve assembly.
REMEMBER: After all maintenance and cleaning is complete make sure tool is completely dry before reassembly to prevent corrosion and build-up.