Remove
the four screws hold the knob housing to the chamber assembly and pull the
knob. . Be careful when you pull the knob off as two small brackets will
fall out. These fit under the bottom edge of the knob and control the turns
of the knob. 
Sextant
is shown on its side. Unscrew the piston adjuster counter clock wise and
remove. Then remove the 8 screws that hold the chamber cover.
Shown
is the chamber after removing the 8 screws. You will have to experiment
but fill the chamber about 1/8 full. Some of the fluid will drain into the
hole on the bottom of the chamber. Before you refit the piston
you might stretch the spring slightly for a better feel.
Replace the piston, and secure the cover with three screws for your test. If you get a bubble then reassemble. If not then experiment some more with the fluid level. If you can not get enough fluid into the chamber then go and look at the assembly on page 1 and 2.