John Deere L120 wiring diagram

check wiring and switch at and for pto

Just out of curiosity check your pigtail that plugs into the pot harness. I have ran into a broken wire inside that pigtail before.

Type into google john deere riding mower wiring diagram for pto switch clutch circuit then click images

check the fuse if ok check the safety switches

You have several safety switches on your unit. The engine should not start if the PTO safety interlock is engaged. Be sure PTO switch is off.
If the sarter Does Not Work Or Will Not Turn Engine Brake pedal is not depressed.
or the PTO is engaged.
Battery terminals are corroded. or Fusible Link in starting circuit is blown - (Not likely unless bad wires) Here is a link to your wiring diagram (maybe your model)

http://www.postimage.org/image.php?v=Pq1tOfiS
Notice how the starting circuit goes through the brake pedal (must be depressed) and the PTO switch (must be disengaged) and that the PTO only works with operator present. Print that page while link still works.

Park brake switch is the most likely culprit,any other would cause the tractor to not turn over in the crank position.

sounds like the seat switch is bad

have a john deere zero turn that will not turn all the way over