NGK Standard Spark Plug
CPR6EA-9S / CPR6EA-9 (hotter)
Fits the Honda CRF110
- The NGK Standard Spark Plug is the workhorse at the heart of smooth-running engines around the world.
- OEM quality.
- Triple-gasket sealing process.
- Consistent performance.
- Sparkplug of choice in millions of vehicles.
- NGK is the world's largest supplier of OEM spark plugs.
- Tolerances are so close that the margin for error is near zero.
Note: The higher number plugs are colder plugs. These are used to prevent knock on higher compression setups. More info can be found below.
HEAT RATING AND HEAT FLOW PATH OF NGK SPARK PLUGS
Some basic structural factors affecting the heat range of a spark plug are:
Surface area and/or length of the insulator nose
Thermal conductivity of the insulator, center electrode, etc.
Structure of the center electrode such as a copper core, etc.
Relative position of the insulator tip to the end of the shell (projection)
The major structural difference affecting the heat rating is the length of the insulator nose. A hot-type spark plug has a longer insulator nose. The insulator nose of a hotter spark plug has a longer distance between the firing tip of the insulator and the point where insulator meets the metal shell. Therefore, the path for the dissipation of heat from the insulator nose to the cylinder head is longer and the firing end stays hotter. The insulator nose of a hotter spark plug also has a greater surface area that is exposed to more of the ignited gases and is easily heated to higher temperatures. A colder spark plug functions in an opposite manner.
The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, then serious trouble can be the result. The optimal firing end temperature is approximately 500°C (932°F) to 800°C (1472°F). The two most common causes of spark plug problems are carbon fouling (< 450°C) and overheating (> 800°C).