There is a "locking" circuit on the mower motors, the switch just activates one of the solenoids under the seat so that it locks in - that's why it's a momentary switch so you need to check that.
FWIW, those mower connectors aren't too good, I replaced them with heavy duty terminal strips and fork terminals on the wires.
I'll take a look, may have the belt number in my book. wombat ron, there