The other day I began the work of getting my carb. I was able to get the tank off, but I couldn't figure out how to remove the fuel line where it wouldn't drain the tank. I just pulled all of the vacuum hoses off and left the fuel line hooked up. I laid the tank on a box to the left of the bike. What position should the petcock be on so no fuel will drain out? I tried it on PRI and it flowed like crazy. What's the trick on this one?