Follow the cable down to the motor. You will see what the cable hooks on to. If that lever is not permanently attached to the rod, then you can loosen the bolt / take off the clip, and move it back on the splines to give it a longer pull.
Looking at the fiche it looks like the push plate is adjustable. The fiche isn't very good so I can't be positive but it's worth a shot. Pull the cover for the clutch. In the center there should be either a screw or a bolt sticking out that's locked with a nut. Loosen the nut then turn the center. Turning it in should take slack out of the cable. While you're at it, pull the clutch apart and inspect the steels, fibers, bearing, basket and hub for wear. Also check the basket and inner hub for wear.