It might be the kill switch like Inlet said.
Mechanic might cost more than another good engine.
If you want to try a few things out to save some money try and get it to spark.
No spark could be anything from the spark plug, boot, wire, or the stator if not the kill switch.
On that motor more than likley you push the button to kill the motor unlike the modern ones that are triggered by a lanyard. Is yours a push button?
I don't know how much you know so I'll just throw some stuff out there to save you time.
The kill switch grounds the ignition to the engine block to stall out the motor. The best way to test to see if the kill switch is the problem is to disconnect it and see if you have spark. Can you find the wires to the kill switch?
If so disconnect the wires on the kill switch and isolate them so they do not ground out and then check for spark. Do not hook up a gas line.
BTW, how are you checking for spark? If you are pulling out the spark plug and holding against the block you might not get a good indication and could get zapped. You should also leave the plug in the head so when you pull the starting cord you get actual starting conditions. If you take the plug out there is no compression so when you pull the cord it will spin a higher rpm, the higher rpm might give you spark but when you screw the plug back in you will pull lower rpm's and might not get a spark.
The best tool is a spark tester from your local auto parts store. It's just a simple device that plugs into your spark boot and clips onto your engine block. Make sure it is bare metal that you clip onto for a good ground. It cost around 3-5 $ adjust the electrodes of the spark tester to just under 1/2" (7/16") and give the motor a good pull. The spark should be a strong blue snap. anything else isn't enough to fire your motor.
If you can't get spark after checking the kill switch or replacing the plug and boot you are getting into the stator which isn't all that hard if you like to mess with stuff. Finding a stator for that motor might be the hardest part.
Let us know what you find out.