The plastic nut on the bottom of the bracket tightens the knob end of the cable to the bracket. The knurled collar on TOP of the bracket (directly under the knob) tightens the pinch collar at the end of the cable to hold the choke cable position. If the assembly is still in good condition there may be a rubber cover over this knurled collar/nut and it's not real apparent that this is a seperate adjustment. The rubber cover can remain in place while adjusting the tension. Had this same issue for the longest time and felt like such a goob that I didn't understand this simple adjustment, although it does take a rather specific/determined search through the shop manual (Clymers I think mine is) to find this information. Look at the end of the clutch cable just under the knob and see if you can see what I've described. If you are still having a problem I could either take some picts or copy the info from the shop manual if necessary. I actual unscrewed this knurled collar from the end of the cable before I understood how it worked. I don't recommend this because the "Pinch tabs" that ride inside this collar are fairly small plastic tabs that can be damaged if they do not fit back into their recess properly. I almost damaged mine beyond their usefulness when they were bent out of shape because I didn't understand their purpose. Simply grasp the collar, directly under the knob, and turn it clockwise to tighten. Finger tension is plently and the mechanisim is suprisingly simple and efficient.
