This person is doing a stunt on a motorcycle.
A motorcyclist is doing tricks.
Stunt doesn't imply tricks.
exists e1 x1 x2 x3.(n_person(x1) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & on(x2,x3) & n_motorcycle(x3) & n_stunt(x2))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_trick(x2) & n_motorcyclist(x1))