NGK Motorcycle spark plugs
'When the electrics fail, it's time to dig out some new spark plugs.'
It sounds like something old-timers would say, but a spark plug is an essential part of any combustion engine. And no, in general there's is no digging required. In your motorcycle, there should be at least one per cylinder and it takes care of igniting your fuel mixture. That and compression are pretty essential factors in getting the engine to run.
Petrol engines rely on a spark plug and a spark plug cap to make the ignition happen. Though crucial to the operation of the engine, they often overlooked during maintenance, even thought they are susceptible to wear and tear like everything else. They definitely need to be replaced at some point.
Fun fact: Belgian engineer Etienne Lenoir is generally regarded as the inventor of the electric spark plug in 1860.