Craftsman YS4500 won't turn over

It could be a number of issues. Is the starter engaging? If so it’s most likely a fuel or related electrical issue, possibly a spark issue. If the engine doesn’t crank over at all it could be any number of sensor or electrical modules. To get a better grasp we would need to know the year, make, model of the car and if anything happens when you turn the key. (As in if there is any click, whirring noise, clunking from the engine compartment.)

I guess you were sitting on the seat while trying to start the unit, so Try to apply power direct to the starter, if it turns over buy a solinoid. If it doesn't the starter may be bad. To check the engine: take out the spark plugs and try to turn over the engine from underneath by hand, using the pulley. This will tell if the engine is siezed up

pull the fuel hose and check for fuel flow to the carby
check all safety micro swiitches

Adjust the valves. I had the same problem.

Have you tried bypassing the cut off switch, by joining the wires together

Mine did same thing, need to manually adjust choke. If you raise hood and adjust your throttle you will see that when you press up to choke that it actually hits & pushed in choke. But when you back off if it is like mine the choke doesn't come off, so I manually pulled choke to off & mine started right up. I am still trying to find how or where cable came off for the choke to be adjusted by throttle lever. That is why I was on here looking for photo of engine.

If your starter is turning but not turning the engine over then the "bendix drive" in the starter needs to be replaced. This requires disassembly of the starter once it is off the truck. Usually the best bet is to replace the starter unless it is new in which case the bendix is probably defective.
It's a remote possibility that there may be damage to your ring gear on the flywheel, but that can be checked when you have the starter off the truck. Just look at the teeth in the starter hole and make sure none are missing or chipped or narrower than the rest. They probably are but it doesn't hurt to check. Hope this helps.

You have 3 safety switches located on the tractor, any one of which can cause the tractor to not crank over.
I assume the deck lever is not engaged, you are sitting in the seat and you push the clutch down when trying to start?
Start by lifting the seat and disconnecting the seat switch, push the clutch in and try to start.
Start there and we'll go from there.
Regards,

If you have 3 qts. of oil in your mower, drain it immediately. It only holds 3 PINTS or 48 ozs or 1 1/2 qts. Next, remove your spark plug and put the end away from the hole (to prevent possible arching and fire) and crank the engine over. Probably, a lot of oil/gas will blow out, clearing your cylinder. Clean the plug and try to restart. If it still reaches a point where the engine will not turn past while trying to crank, the valves need to be readjusted. Also check by smelling the dipstick that there is no gas mixed in the oil. That would mean your carb needle and seat are leaking.

Hi
Starter drive is stuck. Clean by spraying brake kleen on starter drive and blow drive with air. Might
have to remove starter to clean. Check for missing cogs on starter drive.