The motor must turn in 2 different directions on this model for it to operate properly. One direction is for spin, the reverse is for agitation. This is controlled by the timer. If a timer contact goes bad, it only sends partial current to the motor, causing it to hum, but not start.
My usual finding in these situations is a bad timer. It is also possible, but very rare, for the motor to have a broken wire on the harness, so it pays to lean the unit back and remove the bottom panel to inspect this.
[ June 09, 2002: Message edited by: Jim- The Virtual Repairman ]