Remove the carburetor from the engine by removing the screw or bolt holding it in place. Unscrew the float bowl from the carburetor by removing the screw or screws holding it in place. This will reveal the float and needle, which you can remove by hand along with the bowl. Remove the high-speed gas jet by pulling it out of the passage in the center of the carburetor by hand.
Enlarge the high-speed jet passage using a drill, if necessary, to accommodate the propane jet. Use a drill bit one size larger than the jet's diameter, to make room for the connecting tubing.
Install the propane jet by inserting it into the passage where the high-speed gas jet was located, and attach flexible gas tubing so it connects the end of the jet to the adjustment valve. Push each end of the tubing onto the appropriate connection, then apply sealant around each connection to ensure a tight fit with no leakage.
Connect the adjustment valve to the propane regulator with tubing, then install the emergency cutoff valve at the other end of the regulator, again using a short length of tubing to connect the appropriate ends. Apply sealant to the connections.
Run more tubing from the cutoff valve to the propane tank's output valve. Seal the end that connects to the cutoff valve.