Does the wire lead to a box that says "Series 4" or similar? That's the kill for the deadman, When the deadman bar is released it grounds out the coil as well as applys a brake to the flywheel.
Probably gummed carb. Pull the carb off the gas tank and check if the intake tubes are plugged. I may have an old filter box in my pile of junk that you can have for the shipping charge if interested.
Once that starts seizing up it has to be replaced. The ratchet balls eventually wear grooves in the housing and bind up the works. It's about $15 and you need a special tool P/N 19244. All ya do is take off the cowling, remove and ground the spark plug wire, block the blade then unscrew it using the special tool. Installation is reverse but ya torque the clutch to 55 ft.lbs.
Nate