This happened on my WR. It was because the tab on the starter lever was not lineing up right with the tab on the foot peg. Plus the tab on the lever was half worn off from using to much leg and hitting the peg to hard. The starter lever was getting wedged inbetween the frame and the peg if I used any inward pressure on it. Check the alingment of the were stop tabs on the peg and the start lever, I used a section of black hearter hose on the kick start lever and covered it with heat shrink. It is wearing out but its cheaper than replacing the lever. If this is the case,
1, seek a half decent welder to weld a extension plate on the foot peg stop
2, try to tell him not to kick it so hard. I am still trying to learn step 2 :) .