1987-2004 Kawasaki Mojave KSF250 Service Manual, Page 197Get this manual
APPENDIX 163 Spark Plug Condition
Carbon Fouling
Oil Fouling
Normal Operation
Overheating
Spark Plug Inspection -Remove the spark plug and inspect the ceramic insulatorWhether or not the right temperature plug is being used can be ascertained by noting the condition of the ceramic insulator around the electrodeA light brown color indicates the correct plug is being usedIf the ceramic is black, it indicates that the plug is firing at too Iowa temperature, so the next hotter type should be used insteadIf the ceramic is white, the plug is operating at too high temperature and it should be replaced with the next colder type