The main drive belt/chain may be broken or jammed.
replace it
get a new one
There could be many reasons why your Sears riding lawn mower won' shut off. The key could be jammed for example.
because it needs a 1600 vee dub engine in it to make it go faster to have lawn mower races
Try pulling out the spark plug and clearing the cylinder
your electric motor(I assume) probably wont have enough torque, That is on a Riding type mower, not a push mower, it might work on a push mower as long as its not self prepelled, because your motor probably still wont have enough torque!
not getting gas. clean\carb rebulid needed
It is impossible for any bird to fly directly backwards. Unless the wings were put on backwards it wont work, as the wings are designed to propel forward.
Perhaps it is the starter drive. That happened to my riding mower. Got the drive replaced, works fine.
Your flywheel key might be sheared
There are way too many reasons for a mower not to run. Without more information it is impossible to diagnose the problem. If you still want help try asking again with the make of mower, the engine, details of what you have done and what the symptoms are.
did you check and make sure you have plenty of oil. or maybe your lawn mower just needs a break.