This one tests the Hall sensors, and combined with either a dial guage, or a digital caliper can also be used to set the timing. It is based on the tool mentioned here, http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/electrical/Hall_sensors/Hall_sensors.htm , with the addition of a two way switch and the plug from the loom that the hall sensor plugs into, enabling me to test both sensors with a flick of the switch. It draws it's power from the ACC plug on the bike, saves having to have a separate power supply.