Motorcycle Repair: petcock and fuel lines on 1972 Honda SL350, old bikes, petcock

Question
My bike: 1972 Honda SL350. I'm confused.  My bike will not start (old fuel from last season I think)and I think something is odd about the petcock.  I disconnected the fuel lines at each carburetor with the petcock in the off position (3 o'clock). No fuel, of course.  Then I turned it to "on" (6:00) and gas came out only one line. And when I put it on reserve (9 o'clock)the flow in the previous one stopped, and the other started.  What gives? It's like only one carburetor would run on "on," and only the other one on reserve.  Or am I missing something?

Answer
That's not right.  Try putting your finger over the one that is flowing and see if fuel doesn't come out of the other hose.  Both lines should flow at the same time in either the normal or reserve petcock position.  Those were neat old bikes, hope you get it going.

Good Luck
Rich