Its deffinatly something with the cable, wether adjusted incorrectly, incorect mounting piece, or stretched cable. It sounds like it is too tight by the description, like the lever on the motor isnt returning all the way. An easy way to tell if it is cable orientated, disconnect the cable, and have someone give you a push to get rolling, then shift into gear. If the clutch dosent slip, you know it had to be the cable. If it does, then its something under the right side cover. Good luck!
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