I know on many of the carburator caps, there is a little "c" clip that holds is onto the end of the cable. It would either be on the upper or lower side of the cap, most likely the lower. Take the slide and spring off the cable, and look at the bottom side of the cap. You should be able to get it off with a little screw driver or somthing. Good luck, and dont cut the cable.
THE 80's RAGE! Currently owns:
81, 85 Yamaha Tri Moto 125
83 Yamaha Tri Moto 200 x2
82,83 Yamaha Tri Moto 175 project
85 Yamaha Tri Z 250
84 Kawasaki Tecate 250
84 Honda ATC 70
85 Honda ATC 350X
84 Honda ATC 250R
(2) 84 Honda ATC 200x
82, 83 Honda ATC 185s
81 ATC 200
Lots of other parts and bikes