What are the symptoms of a bad motorcycle spark plug?

[BellaLee]

Symptoms indicating a faulty motorcycle spark plug requiring replacement: difficulty starting, reduced power, excessive exhaust emissions, increased fuel consumption; severe spark plug damage with signs such as blistering at the tip, black streaks, cracking, or electrode melting. Methods to determine if a spark plug is damaged: Remove the spark plug for visual inspection and assess its condition based on the following color observations. A normal spark plug will have an insulator skirt and electrodes appearing gray-white, gray-yellow, or light brown. A properly functioning spark plug will have a reddish-brown insulator skirt, with an electrode gap between 0.8-0.9mm and no signs of electrode burn. If the spark plug is covered in oil or deposits but not damaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged with blistering, black streaks, cracking, or electrode melting, identify the cause of the damage, rectify the issue, and replace the spark plug. Additionally, if the spark plug appears blackened as if smoked, it indicates the wrong heat range was selected or the air-fuel mixture is too rich, with oil seepage.