1995-2004 Kawasaki Lakota 300, Lakota Sport, KEF300 Service Manual, Page 241Get this manual
APPENDIX 15-3
When plug of the correct heat range is being used, the electrodes will stay hot enough to keep all the carbon burned off, but cool enough to keep from damaging the engine and the plug itselfThis temperature is about 400 800C (7501,450F) and can be judged by noting the condition and color of the ceramic insulator around the center electrodeIf the ceramic is clean and of light brown color, the plug is operating at the right temperatureA spark plug for higher operating temperatures sometimes may be needed for severe conditions, such as continuous high-speed riding, or towing heavy loadsSuch plug is designed for better cooling efficiency so that it will not overheat and thus is often called "colder" plugIf spark plug with too cool heat range is usedthat is, "cold" plug that cools itself too well,the plug will stay too cool to burn off the carbon, and the carbon will collect on the electrodes and the ceramic insulatorThe carbon on the electrodes conducts electricity, and can short the center electrode to ground by either coating the ceramic insulator or bridging across the gapSuch short will prevent an effective sparkCarbon build-up on the plug can also cause other troublesIt can heat up red-hot and cause preignition and knocking, which may eventually burn hole in the top of the piston