The next step would be to open up the tach case and clean out any oil grease/oil that may be causing the problem. Then re-lubing the bearing and closing it back up. You will have to cut or de-crimp the chrome band to get at the insides. Cutting it is easier and faster. Then drill small holes in the cut ends and wire twist it back to tight. Don't get any cleaning solvents on the face or dial, it will melt the plastic.
I found that out the hard way the first time I tried to clean my speedo. I ended up with a nice, clean, numberless speedometer.