Garden Tiller Tines Stopped Turning?

Assuming that the engine kept running when the tines stopped turning:
(1) are you sure that the gear selector was in the correct position to engage the drive to the tines and not just in forward motion (self propelled Tiller).
(2) The tines are secured to the drive shaft by shear pins. i.e. a pin which is designed to shear off, if excessive resistive torque is applied to the tines (e.g if the tines get jammed against a big stone or something). Some rotavotors would have the tines on separate sleeves with 2 separate shear pins).
The machine would probably have been supplied with 2 spare shear pins -and they are very easy to replace.
You might be tempted to replace a sheared pin with a bolt or other pin of the same diameter. Don't! The bolt you use might be far stronger than the proper shear pin and will result in worse damage to the rest of your machine.

JD
May 2008