Another way bad spirits can hitch a ride is if your passenger footpegs are down, but you do not have a passenger. Spirits apparently view this as an invitation to hop on board and cause trouble. It's not clear how well a guardian bell works in this case. Also not clear is how it interferes with this being a common practice in a funeral motorcade. Since having your pegs down invites spirits, this is actually an open invitation for the spirit of the deceased to hop on and join you for one last ride.