I would double check that your PTO lever is parked. If so, look underneath the dash at the lever and see if the paddle on the lever is contacting the plunger of the safety switch.

Sorry to be so ignorant, but is the PTO lever the one that engages the mower blades? If so, it is parked. I did manage to get it restarted by fiddling with all of the controls, including the choke, which may have a safety switch; I haven't figured out which one was causing the problem.

You will need the full model number and serial number to find the exact manual, and if you're looking for a service manual it will cost you $40 to $60 bucks. It's a 234 page manual mainly showing exploded part diagrams, replacing parts, parts locations, wiring diagram, specifications and rebuilding the transaxle, engine and deck. Good luck finding a free download for a service manual but you may get lucky. A operator's manual are always free from john Deere but little use for troubleshooting problems.

When a machine won't crank (start would mean it turns over but won't run) It's because of no voltage or one of the three safety switches are not closed and locking out the starting circuit. Tom's comment would be the most obvious unless you weren't sitting on the seat or didn't have the brake engaged, all three have safety switches. Your machine will not start if the deck is engaged so the PTO must be parked as Tom stated.

The snap you heard was probably caused because your deck blades jammed on dirt or a grass clump backing up which fully extended the extension spring on the deck and locking up the motor causing a stall. When the motor stalled the extension spring snapped back the idler and extension arm when torque was removed. SNAP!

Thanks, Kevin. I was only looking for the operators manual (I saw the available of the service manual, but I'm not interested in that - I'll take it back to the guy I bought it from who did the refurbishing). I think one of the safety switches must be a little flaky, because if I move them back and forth, eventually it will turn over and start.

Got it working last fall and also this spring, but I had to fix one of the front tires, so I jacked it up, and now it won't crank again. I followed Tom's comment and looked under the hood. I assume the PTO lever is the same as the "attachment engagement lever". I moved it so that the plunger is fully depressed, but still nada. Is there a safety switch on the throttle/choke lever? When it was working, I had to carefully fiddle with it; there would be only one position where it would crank, but I can't see any electrical switch there.