You won't need to connect this timing light to your engine's battery.  This timing light is entirely self-powered by 2 "D" cell batteries.
 
Useful in checking for "no spark" conditions
Built-in flashlight; convenient for dark engine compartments
Works on 2 or 4 stroke engines; all ignition systems (including magento)
Xenon flash tube generates bright flash, visible even in daylight
Lightweight design is ideal for field or shop use.
 
Part # 99998T120M