JMH, One thing I have done numerous times to provide a temp gas supply for testing or sometimes to get a old machine home until better things can be done is to:
1) using an available fuel container that can be supported higher than the carb.
2) put enough fuel in the container to have 3-4 inches above the bottom
3)I like to use a clear hose so I can prove that fuel is flowing-start a syphon then close off the lower end never letting it lose its filling of fuel.Also the clear hose lets you see when you have drawn enough fuel up the hose to fill it but not give you a drink.You really have very good control of the filling of the hose when you can see the level in the hose and modulate your oral vacuum.
Good luck and be careful.
4)connect the lower end to the carb inlet and the syphon will keep the carb fed very well for stationary running
5)Fuel in the container needs to be above carb inlet

Caution: Avoid spillage-do not use a container with a large opening-preferrably just large enough to admit the hose-let any spilled fuel evaporate well before trying to start or make sparks-do this outside and prepare for worst case problems.

Bob Taylor