How do you check if the coil is operating on a Honda CRF 230?

Put the bike in neutral gear and switch the ignition on. Remove the spark plug from the cylinder head. Hold the spark plug against the engine so metal touches metal. Crabk the engine. If you see sparks in the spark plug head, then the coil is at least operating. If there is no spark, the spark plug itself may be defective. The spark plug cap may also be defective, try to change this. Check the earthing point of the coil, is it loose or not properly connected? Check if the battery is fully charged. The coil can fail in two ways, its voltage may be too low or none at all. The voltage at the coil as measured by a multimeter should be 70 Volts up to a 100 Volts. You have to change the coil if you have ruled out other things, such as a weak battery, loose connection, a bad spark plug or a defective spark plug cap.