The ignition coil on a motorcycle serves to step up the relatively low battery voltage to the high voltage needed to fire a spark plug. Coils are generally a sealed, water-tight component. As such, they are generally not a repairable item.
Routine checks on a coil are not necessary. They should be tested as part of a troubleshooting procedure whenever the motorcycle becomes difficult to start or runs rough. Testing them tends to be relatively simple and involves the use of an ohmmeter.
Turn off the motorcycle ignition.