I bought a RVF and the bike came disassembled so I have been putting git together and there's a few things I am not sure about. The first thing is the petcock. I see it has a diaphragm on one side with an outlet. Does that outlet need to be hooked up to a port on the intake for fuel to flow out of the petcock? I put some gas in the tank and turn the petcock to the on and reserve position but no fuel will flow from the petcock. I took it apart and there is not obstructions and it seems to be working properly.

The second thing is that it leaks but I can't tell where from.

video of leak

https://youtu.be/cvrnGltEo1w

Yes needs vacuum pipe connected for fuel to flow with running engine unless diaphram faulty or bypassed it's hard to tell from video where leak is coming from could be rubber o ring on tap where it seals against tank or possibly the tap itself if it's been taken apart at some point or even the tank itself if rusty they tend to rust around the lowest point around where the tap bolts on a small pinhole can give a big leak.

Thanks, there is no rust on the tank. I took the petcock back off and inspected the tank. It's in excellent condition. Hopefully it's jus the O-ring

Whilst you have the tap out have a probe with your finger inside the tank around the plate where the tap bolts onto if clean no gritty residue then probably just a new o ring required.

Yes, I checked it. It's very clean inside.