Wrong Side of the Tracks
Most people seem to have trouble once the bike scene starts and you have to drive along side the train. Don't do that. Get the bike as far ahead of the train as possible, as fast as you possibly can. Once the first turn in the tracks starts, you should see a small ramp over to your left. It's near a group of motels. Take it and ride up until you're on a metal railing that runs right beside the train. As soon as the train begins to pass you, turn and try to drive/jump the bike over on top of the train. Now you'll still have to use the gas just as if you were driving on the ground in order to stay on top of the train. If you stay on there long enough, Big Smoke will kill the 4 enemies before the train even gets to the first long tunnel.
Added by: Forgoten_Scars Nov 15th 2011, ID#8112