Checking for spark on your motorcycle can be a hair-raising experience—literally—if you aren’t careful. The time-honored method has been to hold a sparkplug in your hand while grounding it to the engine as you either push the starter button or kick the bike over to see if you can spot a blue arc across the electrode gap. There has always been a shock hazard, and it’s only gotten worse with the high-voltage ignitions used on most bikes today. But even your old magneto-equipped machine and its relatively tame 10,000–15,000 volts can give you a zap to remember if you aren’t careful.
Which is why it’s not a bad idea to have an in-line spark tester in your toolbox. The ends of the tool are configured like the top of a sparkplug. One end is attached to the plug wire from the coil (or the on-plug stick coil if the bike is so equipped), and an included lead completes the circuit from the tool to the sparkplug. In between is a clear housing with a lightbulb inside that flashes when ignition current is sensed. It’s a simple and hands-free way to check for spark, eliminating potential shocks. The flash of the light is also easier to see than the actual spark, especially in bright light.
This tool can also be useful for a rough check of spark timing, at least on a single-cylinder machine. Simply leave the sparkplug in place, hook up the test unit, turn the engine over and see if the light flashes as the piston runs up on compression.
The Lisle 20610 spark tester pictured here lists for $13 and can be plugged into your vintage magneto or the high-tech stick-coil on the latest sportbike. Heck, even the Snap-on version of this tool is just over $16. It’s cheap insurance against being zapped.
