Spark plugs that haven't been changed for a long time can become one with the cylinder head. Fortunately, it's possible to repair damaged threads instead of scrapping the head.

A clogged silencer and fuel screw adjustments bring the engine to life. With a clean spark plug and proper idle speed regulation, the Honda Dio AF 27 is running smoothly again.

Let's say you've just removed an old spark plug. Does it have any life left in it? Can it be reused if it is cleaned properly? Let's take a closer look.

Hand-thread the spark plug back into the engine, being very careful not to cross the threads. Then tighten the spark plug, but don’t over-tighten it or it’ll crack.