This spark plug color chart will help you determine if your motorized bicycle engine is running too cold or rich, or too hot or lean. Simply compare the color of your spark plug with those shown on the chart below. Click the Download button for a higher resolution uncompressed image.
Reference: https://motoredbikes.com/threads/tuning-plug-color.58000/post-529953
Reference: https://motoredbikes.com/threads/tuning-plug-color.58000/post-529953
