I looked at your photo (attached) and everything is basically hooked up correctly. The cable could have a little less slack in it, but at the position shown the motor is at idle position. With the motor on the tire and the tire on the floor at idle, is the roller spinning/moving? If it is, then the motor is not all the way down on the tire. If the motor is on the tire and the tire is on the ground and the roller is not spinning and the motor is racing, then I'm lead to believe there is a problem with the clutch, like fuel mixture getting onto the clutch pads through a broken seal on the bearing (not the lipped oil seal that's pressed in to the crankcase, but the shield/seal on the bearing itself.)
ps your Solex looks beautiful.