Complex sentence: During the high-speed pursuit, the helicopter accidentally crashes and explodes and the two then ditch the damaged motorcycle and hop on a train on which, coincidentally, the same two bikers whose machine they had "borrowed" are riding.
Split into simpler sentences: During the high-speed pursuit, the helicopter crashes and explodes. The two ditch the damaged motorcycle and hop on a train on which, coincidentally, the same two bikers whose machine they had "borrowed" are riding.