I have an L120 lawn tractor which works perfectly except that when you engage the pto to turn on the cutting blades it burns out the 20 amp fuse which shuts off the engine. What could be causing this? Could it be the clutch?

Could be the copper windings in the coil shorting out .
Unplug the clutch , pull the switch see if it stills blows fuse l
If not clutch , if so switch ,
Luck

Hi,
The switches are notorious for causing this.
Peace,
Clarke