Shaun,

i think I know what you mean, but it is not a hydraulic line and I doubt that it is bronze. I think that you are talking about the scavange tube that runs from the bottom of the air intake just before the carburator. Though it is not really necessary (the early model engines did not have one.), it should be easy to replace. I have a late model carburator on an early model engine so I am not sure what the original factory part was, but you can use copper tubing and standard fittings available at most hardware stores to make your own.

John