I went to look at the bike that I'm considering buying again, and started noting the things I needed to do to try to start it. When removing the tank, I first turned the fuel off. When I turned the petcock to the OFF position, I heard a tiny click. I now cannot turn the fuel back on, the valve won't turn. Is there a trick? Do you have to push or pull on the knob? I was afraid I would break it, so I thought I'd better ask the group.