Leaky petcock

[JARichmond]

Hey everyone. I'm looking to get a bit of advice regarding my new-to-me petcock. It's the same style that are on many of our bikes. I replaced the last one because it had developed a leak and I needed to replace the o-rings, so I bought a new one from a salvage yard as the rebuild kit was actually more expensive.
When I installed it, the new petcock didn't leak at all, and produced an excellent seal. Unfortunately, when I ran it an hour later, it decided to start leaking again. But that isn't my issue, as my carbs are great and shut off the fuel before flooding the engine. What I'm concerned about it what I saw when I replaced my vacuum line with clear PVC. I figured it would look a bit better, and wouldn't be an issue because it's only handling a vacuum. What actually happened was that I'd get a bit of fuel running through the vacuum line. It's not too much, but it seems that it will hurt my fuel economy significantly. I want to fix this ASAP, but don't have time to buy another petcock only to find out it, too, is leaking (nor does my wallet support it).
Are there any methods you can suggest to test a petcock in the future? It held a great seal for a while, but all of a sudden seemed to give out.

CLIFF NOTES:
-replaced bad petcock with new one from wrecker
-held up great for a while
-allows fuel through vacuum tube
-looking for ways to test petcock next time

 

[226dark]

I replaced the last one because it had developed a leak and I needed to replace the o-rings, so I bought a new one from a salvage yard as the rebuild kit was actually more expensive.

Not sure. Check your fuel economy. It is being drawn all the way to the intake?
Sorry to say, buying a rebuild kit is new, buying from wrecker is 30 years old and may now need new rebuild kit anyway.

 

[JARichmond]

Well it's running through the vacuum line and I noticed it bubbling at the intake boot, the spark plugs are also black as night so I assume it's making its way through the intake. I can't comment on how my fuel economy is actually doing as I don't have it registered with stickers yet. But having that much fuel going into the cylinders can't be good.