This video to explain how the valve works on a beam type regulator used on a natural gas or propane engine. These units are used often on emergency generators. I do not sell these regulators but have some to experiment with converting gas engines to run on Natural gas or Propane. This is a model 039121 regulator it has a manual primer. Pushing the "prime" button allows gas to flow through the unit and thus fill or flood the venturi carb area with propane or natural gas to allow starting. With a pull rope start engine a manual prime often is required. With an electric start engine if the rpms are high enough a manual prime might not be required. There has to be enough vacuum from the venturi in the intake carb area to open up the beam balance on the regulator. There are many diagrams on the web explaining how this type of regulator works and videos showing them in operation.