The choke cable is held in place in the carb by a plastic nut. Simply unscrew this and the plunger, etc. will pull out. Once it's in your hands it will all be obvious.
When you are dismantling it all, be very careful not to lose the little circlip that holds the plastic section on the cable.
Cheers
GC
p.s. Do me a favour, if you still have an NSR125, can you measure the fork diameter, distance between the fork centres (on the top yoke) and, if possible, the offset of the yoke.