I cant shut off my lawn tractor with the key

my specialty,but,you didnt post what the problem is,so,here goes,if it wont start,it is probably a bad safety switch,take the small black wire off of the coil,if it starts,then its a safety switch,if it doesnt then it is the coil,if it only clicks with a charged battery,it is the solenoid,turn on your key and short between the two big bolts on it if it starts it is bad,if you need a belt,i will need the numbers under the seat,otherwise i will try to find them for you,i will post a user manual for you here, Murray 425607x52A 42 34 Lawn Tractor Parts
Murray 425016x48A 42 34 Lawn Tractor Parts
Murray 425306x48A 42 34 Lawn Tractor Parts
Murray 425600x48A 42 34 Lawn Tractor Parts
Murray 425618x48A 42 34 Lawn Tractor Parts
Murray 42560x52A 2000 42 34 Lawn Tractor Parts
Murray 42820x24A 1996 42 Inch Cut Lawn Tractor Parts
Murray 425619x24A 42 34 Lawn Tractor Parts
a few manuals,find yours here or go here to find it by the numbers under the seat,all part numbers are in them, Search eReplacementParts com

The electrical part on the bottom of the carb is a fuel shut off solenoid. When you turn the key on, the plunger inside this mechanism retracts, allowing fuel to enter the carb. If you remove this it is easy to bench test with an alternate power source. Hope this helps.

I’m happy to assist further over the phone at https://www.6ya.com/expert/layne_0fccff498c319c32

You most likely have a piece of debris stuck between the needle and the seat inside the carburetor.

All the ignition switch does is complete the circuit or break the circuit. It sounds like in this case the circuit is completed all the time. Try unplugging the wire plug from the new switch while the motor is idling and see if the circuit is broken and the engine shuts down. It could be you got a bad switch from stock. Rare but it happens.
Bruce

OLDER SEARS TRACTOR WILL NOT SHUT OFF WITH KEY. STARTS FINE.. ANY IDEAS WHAT TO LOOK FOR?

Under the cover that covers the flywheel on the right hand side there is a connector that is likely unplugged,this grounds the coil when you turn off the key and there by shuts of the motor.If this is not the problem then you likely need a new ignition switch.

Sounds to me as if the replaced coil might of fried when you shut the tractor off, several older lawn tractors have a coil that has just one wire going to them and this is grounded out by the key switch to shut the tractor down what happens is when the key switch gets warn it sometimes will feed 12 vdc or battery positive power to the coils instead of shorting it out in which case when you replace a coil in a lawn tractor it is best to replace the ignition switch along with the coil. If this is not a electrical problem it could be as simple as a plugged fuel filter that juat happens to let enough fuel thru as it sits to run for a little while but not enough to run fulltime. Hope this Helps, Don

the ignition switch grounds the coil in the off position.repace the switch

check your crank case for fuel,
bowls stick open an fills it up
if this is the case , you can buy a plastic fuel cut valve from lawn mower shop
todays fuel isn't very good
also try sta-bil fuel coditioner

if it is an diesel mower - it will have a fuel cut off switch on engine.