A bicyclist in a white shirt and black shirt is fixing a bike on the sidewalk while other look on.
The biker is fixing the chain on his bicycle.
Although the bicyclist is fixing the bike, nothing in the first sentence infers that the chain is the part that is being fixed, as opposed to some other part of the bike.
exists e1 s1 s2 s3 x1 x2 x3 x4 x5 x6 x7 x8.(n_look(x8) & n_sidewalk(x6) & a_on(s3) & Manner(e1,s3) & while(e1,x7) & -(x7 = x8) & n_look(x7) & Theme(e1,x5) & Actor(e1,x1) & v_fix(e1) & on(x5,x6) & n_bike(x5) & in(x1,x2) & n_shirt(x4) & a_black(s2) & Theme(s2,x4) & n_shirt(x3) & subset_of(x4,x2) & subset_of(x3,x2) & a_white(s1) & Theme(s1,x2) & n_bicyclist(x1))
exists e1 x1 x2 x3.(n_bicycle(x3) & of(x3,x2) & n_male(x2) & n_chain(x2) & n_biker(x1) & on(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_fix(e1))