The needle bounces a little bit. No real movement when I rev it. Bounces erratically when idles, up to 3000 and down, but no real reading. Checked all connections, cleaned and greased. Also check black to the coil and greased it. Still same thing. I did notice when I was taking it apart the metal bracket is broke, thought it was just loose, so I put a washer in it to stiffen it.. Obviously was hit. Temp gauge is fine, so do I need to replace the tach? How can I tell if it is the coil? Seems to be running fine. I am so confused.