A man riding an unsual bike in a bike race.
A man is racing his bike.
The man is riding a bike in a bike race but that doesn't necessarily mean that he is racing his bike.
exists e1 s1 x1 x2 x3 x4 x5.(a_topic(x1) & in(e1,x4) & n_race(x4) & of(x4,x5) & n_bike(x5) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_bike(x3) & a_unsual(s1) & Theme(s1,x3) & (x1 = x2) & n_man(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_race(e1) & n_bike(x2) & of(x2,x1) & n_male(x1) & n_man(x1))