Same issue on a broken bike someone gave me. Have to take off both plastic sides. On the left side, there was a rubber leader that had rotted and broke (it attached the servo motor to one side of the kevlar friction belt). This part may work if your rubber leader broke too. I'd call first to make sure it comes with the rubber leader although it does look like it from the picture: http://www.sportsmith.net/itemform_part1.aspx?item=P1361243.
I didn't want to pay the price so I replaced my rubber leader with plastic pipe hanging strap. I cut three pieces the same length as the rubber leader, drilled holes and put it in the same place. You may have to turn the servo motor by hand to get the screws/bolts in the correct position. Don't try to straighten the kevlar belt if you happen to remove it. The instruction manual states it may make the layers separate.
Also, you may have to calibrate the bike after this procedure. I don't know but didn't really care ... I just pedal at a resistance that feels good and don't really look at the calculations. Calibration instructions are in the maintenance manual you may have with the bike.
Paul, October 2010
