That doesn't sound right. Putting risers on should have made the cables tighter. I would carefully check the routing and position of the cables before making any adjustments. There are two adjustments on the cables, one at the bar and another further down the cables.
Be careful not to take out too much of the play at the hand grip and check with the motor running at idle and turn the bars from hard left to hard right to make sure the idle doesn't change.
The cables need to route through their holder under the R bar, through a wired holder that attaches to the back of the top fork pinch bolt, and then under the top bridge and to the inside of the R fork.
If all that is correct, make sure when you release the throttle, when at operating temp, you can hear the trottle plates snap closed when engine is turned off. If you can, adjust the cables as needed. I would adjust the one on the L-side of the steering head first, and fine tune the adjustment using the one at the throttle grip.