I recently purchased a Honda Harmony 215 SX. I took the rear wheels off to clean inside. I removed the outside bolt holding the wheel and then pulled the wheel off. Underneath is a drive gear attached to the drive shaft. I pulled the snap ring and washer holding the drive gear to get a thorough cleaning. When I installed the drive gear, I accidentally installed the key that goes between the drive gear and shaft, backwards. This kept the wheel from spinning freely in either direction. I removed the wheel and drive gear again and turned the key to the correct position. When I put it back together, it worked perfectly. BTW......the key is a half circle shape and the flat side must be facing the drive shaft with the arc side facing the wheel.
Mike M, June 2008