This is a single cylinder engine with a mechanical governor....no stepper motor on board, so don't be looking for that.
Take a jumper wire and connect it from the positive side of the fuel solenoid to battery positive. You should not hear or smell any gas flow. If it does flow it will be coming into the carburetor (mixer), and may be muffled and hard to hear or smell. If it does flow, you have a stuck or damaged valve inside the demand regulator. If it is all quiet, which is good, with some vice grips and two flat pieces of strong metal, kink the the fuel hose above the demand regulator. Energize the fuel solenoid and leave energized. Take a dull tool such as a 4 mm allen wrench or smaller and press the diaphragm through the cover. No fuel should flow. If you feel it blowing past your wrench while pressing, the diaphragm is perforated. (Be sure your pliers are extremely tight; it's hard to smash those hoses. Gas flow at this point may be making it past your kink.) So in the first test you've checked for proper closure of the diaphragm valve, and in the second test you've checked your diaphragm for holes or cover gasket leaks.
State your problem, not your diagnosis.