I just cleaned all the sludge out of my V-Star gas tank by allowing a sludge eating solution to soak in it for a while. Then I shook it like a hooker that owes me money. To plug the hole for the petcock I used card board. Yep, you read that right. I cut a piece of card board to fit, then punched holes in it for the crews with a hole puncher. I then smeared a generous portion of blue RVT sealant all over it on both sides. I then pushed the sealant into the sides of the cardboard and inside the holes I punched. I completely sealed the cardboard from every angle. I allowed it to tack up, and then I screwed into place. It worked great and only took about five minutes to complete. It is a whole lot easy then cutting a piece of medal and locating gasket material. There were no leaks and no residue left behind. It worked great and the tank got cleaned.