There are two Phillips head screws holding the choke housing in place. Removing these makes it possible to rotate the housing counter-clockwise, exposing a small piston. When the piston is fully exposed, the choke shaft can be removed.

A screw on the other end of the choke shaft needs to be removed, and the end pieces pried off. It is important to note how each of the end pieces goes on the end of the shaft--they will need to be reinstalled in precisely the same way.