I recently acquired a used 25011 set. The trolley would not move so I took it apart and found that by loosening the mounting screws on motor assembly it would run but has little power (will not move when body put back on). Voltage to track is 7.4 v.  Have cleaned all contacts, track, etc. New motor needed? Also, instructions says one section of track is an activator track for reversing. Set has 3 straight tracks but all look the same-like regular track. Are activator sections available separately?  Thanks