Motorcycle Repair: fuel petcock positions & startup, float bowls, cb 400

Question
75 cb 400 f (ss) Rick, I'm in the process of the first startup of bringing this old (ss) back to existence.I need to know what each position of the petcock does, also,when I went full choke the first time, I got gas draining from a couple of the float bowls,but, then they seemed to unstick or reposition at the needle seats or something.Should these float bowls overflow with each use of choke ? Old Triumphs proceedure was to push the tickler button as they called them until it flooded the bowl on cold startups' Thanks !

Answer
Bill, there are three positions on the petcock. There's off, on and reserve.  There's a small stand pipe in the petcock the sticks up in the fuel tank.  The fuel will drain down to that level, and when you put it on the reserve position it will allow the rest of the fuel in the tank to drain out.  

The over flow in the carbs indicated the needles and seats inside the carbs aren't shutting the fuel off.  There could be contamination in the fuel lines or the carbs are gummed up so the floats aren't moving freely.  You will probably have to clean the carbs.

Regards
Rich