Tiller: Wheels don't turn but tines turn
If the wheels don't turn but the tines do, it could be that the drives and gears in the transmission that control the wheels have failed. A loose bolt on the transmission pulley also would make the wheels not turn, so make sure the bolt is tight. Check out these repairs that could get the tiller rolling again.
These repairs may help solve your Tiller problem:
Replace the tiller transmission
The transmission controls the motion of the wheels and/or tines on a tiller. An internal gear failure in the transmission can prevent the tines from turning or the wheels from moving. Replace the transmission if it won’t drive the tiller components properly.
Adjust or replace the tiller clutch cable
The clutch cable engages and disengages the drive system on the tiller. Test the drive system and adjust the clutch cable if necessary. If the cable is damaged or broken, replace it.