Your bike has the varible postion slider type of choke.
The thumb lever at the perch is connected to the slide via a cable.
It allows you to close the choke gradually as the bike warms.
The earlier system uses the same plungers and brackets from the rod to the plungers as your later system. BUT the rod and the way it is held is different.
The rod has indents in it with a ball and spring to hold the position of the rod in full and half choke positions. XSJohn used to drill extra indents so instead of only full and half positions you had full, 3/4's, half and 1/4 positions. PIcs in my album (I think).
So to change yours you need the different rod, and some springs and balls.
The spring and balls can be had from grease zerts(gggGary's tip)
The rods come up on e-bay occasionally.