If there is a large amount of carbon deposited on the spark plug of motorcycle, it can be scraped clean with a hard sheet tool, but it is not suitable to use an iron brush.

If there is a large amount of carbon deposit on the spark plug, you can use a fine hacksaw, fine iron wire, small screwdriver, bamboo chips and so on. Go clean it up. Scrape off the carbon deposit and clean up the fine powder and oil.