It vibrates, causes the drive train to move a little. If you want to check to make sure you're not engaged...CAREFULLY try to hold the wheel still by hand. (it should be going slow enough not to scare you) If you can, it's just the vibration. If you can't, you're slightly engaged. Also, to check it, you can put the bike on a level ground, put it in neutral, and see if the bike moves.