On the end of each stock grip there is a little dome. This is actually a plug. Use a sharp object to pry out the plug giving you access to the 6mm (I think) allen bolts. Undo the allen bolts which hold on the bar ends/weights. Throttle side you need to remove the controls (i.e. the housing with the kill switch). Loosen and remove throttle cables (remember which is which) then the grip slides off. Left side easy way=take a knife and cut it off. Hard way is use some sort of lubricant or glue solvant and an air compressor, jam the nozzle in between the grip and the bar and blast away.
Installation throttle side reverse steps above. Left side follow the instructions with the new grips.