i believe the solenoid in question is an anti back fire solenoid that they install to stop the flow of fuel through the carby so it does not backfire when you turn the engine off at higher rpm's. i think it should be wired through the ignition on circuit, which means that when the key is in the on position it gets 12 volts and opens the fuel jet. when power is disconnected it therefore blocks the fuel flow and eliminates any chance of backfire.
this is only from my experiences but i will have a look in my reference guides later for you if you like. i would look now only they are all in the garage.
regards jay
