It's inside the carb......mounted to the underside of the air horn (top section of the carb) and it has 2 wires that exit out of the top of the carb just about dead center and the wires have a black plastic sheath over them.
Here are some pics of it....
The bottom (other end) of the mixture solenoid fits into the recess & hole at the top of this pic.....
More pics of it......
Again, the hole that the bottom of it fits into.......below the center brass jet in the pic.....
The wires & connector (near the end of the screwdriver) for the mixture solenoid.......this plugs into the wiring harness near the front of the carb.....
Here you can see where the wires for the mixture solenoid enter the top of the carb....right above where the fuel enters the carb......
Mixture solenoid is removed from the air horn of the carb in this pic.....