I posted over @ VROC but I figure I would post here too.
I have an '86 VN-750. Just a brief history: I have had the engine out, it has been completely de-EPAed, de-eared, etc.
Late last year I started running into a problem. While the bike was shut off, gas would leak out of the right-side air-filter (remember, my airfilters are attached to the carbs.) Reading up on this stuff, I ran across that the petcock controls the fuel - even though there is no "off switch." So, I bought a rebuild kit for the fuel petcock. While in the process, I figured, why not buy a set of good used carbs. So, I bought a set of carbs that were in really good condition. Got the bike back up and running this weekend, rode around for 5 minutes or so, and I ran into the same problem. When I shut it off, I came back a couple minutes later and noticed gas coming out of the right side carb. (This is the carbs I replaced the originals with. I think they came off of a 95 vulcan.)
In the mean-time, I'm installing fuel shutoff valves to shut the flow of gas off while the bike is not running.
However, my fear is that after riding say 15-20 minutes, the flow of gas into the carbs will outweight the usage of gas, and the carbs will flood, and start pouring out of the airfilter, or down in the crankcase.
I have not checked my float level, but for the life of me can't justify it when it has happened on both sets of carb. I've rebuilt the fuel-petcock.
Anyone have any other ideas?