When your motorcycle won't run, the problem could lie in the spark plug. The job of the spark plug is to ignite the gasoline in the engine, but when the plugs are malfunctioning, so is the rest of the engine.
"Reading" a spark plug can tell you a lot. It is often the only way you can determine what is happening inside an engine.
The color of the insulator tip and buildup on the plug are key symptoms to engine problems.
Remove the spark plug and examine the color and condition of its firing pin.
Look for a black coloration, dry or wet. This would indicate that carbon is attaching itself to the plug.
Check for a glazed appearance on the insulator tip. If it looks like glass, you have a plug that has gotten too hot.
Examine the tip for extra material. Deposits can mean that you need a better quality fuel or that oil is leaking.
Gauge the color of the insulator tip. A yellow appearance means lead is causing the problem.
Check to see if the insulator tip is missing. If it is, this is a sign that the plug is getting too hot.
Look to see if pieces of the plug have melted together. This can indicate that the plug is getting too hot.
