if you have any old motorcycle that uses points type ignition this is a must have tool for setting the ignition timing . this tool is modeled after the factory Honda dealer tool offered in the 60s and 70s ,  it does 2 things it buzzes and the light comes on when the circuit has continuity  so by clipping the leads on either side of the points you can tell the exact position the points open to set the position relative to ignition timing marks on the engine . dont just trust you eye to set timing I 100% guarantee you by the time you see the points open you are way past timing this is a must have tool !!