darn near every savage made has had this problem. this is what you need to do. remove the tank, turn it over and retighten the 3 nuts that hold the speedo tight. put a piece of surgical tubing over the nuts . the tubing worked for me, others in here, use some kind of lock tight stuff. Removing the tank is only a hassle the first time. i can do it now and put it back on in 10 minutes or less.  if you have any questions on removing the tank just ask. the most important thing is too remove all the seat mounting hardwear where the tank bolts to the frame, or its almost impossible to slide the tank off backwards. you have to unhook the electrical connection under the tank in the front before pulling off when you pull the tank off, pull it backwards and to the left.. you dont have to remove the petcock. just the fuel line, the speedo cable where it mounts into the motor(dont lose the rubber washer) and the air tube from the carberator. pretty much it. put some tape along the frame by the petcock so it dont scratch

Someone else posted a while back about using rubber grommets.  I think the size was 9/32".  However, I was in Lowe's today and they didn't have that size.  All they had was 7/16", which I haven't looked at the mounting bolts on the speedo to see how close that size would be on it.