A man wearing a yellow helmet with his visor up rides a red motorbike.
A man is on a motorbike.
A man in a helmet means he's wearing a helmet.
exists s1 x1 x2 x3 x4.(a_topic(x1) & all x5 s2.((n_motorbike(x5) & a_red(s2) & Theme(s2,x5)) -> exists e1 x6.(Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & up(x3,x6) & for(x6,x5) & n_ride(x6))) & with(x3,x4) & n_visor(x4) & of(x4,x1) & n_male(x1) & n_helmet(x3) & a_yellow(s1) & Theme(s1,x3) & (x1 = x2) & n_man(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_motorbike(x2)) & n_man(x1))