Testing cut off solenoid: Get your ear close to carb, have someone turn on the key (Just to on, not trying to start) you should hear a click, which would be the cut off solenoid opening, then have them turn key off, again you should hear click as cut off solenoid is closed.
For intake leaks: I use a spray bottle with soapy water in it, when running or cranking, spray the intake / engine gasket areas, you should see nothing if no leak is present. If leaking it will suck in the soapy water.