Did you lose the spring that pushes on the cut off lever and tapper plate? The spring is basically what makes it semi.
1.) 156A MOSFET with 500 Watt TVS Diode-$15
2.) 156A MOSFET with 500 Watt TVS Diode and 30A Self Resetting Fuse-$18-Out of stock
3.) 156A MOSFET with Active Braking-$20-Out of stock
Shipping cost will be $3
Feel free to message me if you are interested.