When adjusting the throttle cables, the slack is all taken care of with the 2 adjusters on the cable under the bars. The important thing to realize is that on full throttle you want just enough slack in the pull cable so that the hand grip hits the stop and NOT the carb/throttlebody or you will break cables like no tomorrow. If you open the throttle grip fully and slack off on the pull cable just enough so that your linkage down below just misses the stop by a hair, you'll be in good shape and will not break cables. This way does not stretch your cable when ever you twist the grip to full travel.

Also try the forks full left and right with the motor running to make sure they are not too tight and opening the throttle on full rotationl of the forks.