I pulled my fuel tank off my 2001 W650 to clean it out, clean the petcock filters, and change the spark plugs. I was surprised to find NGK CR7E plugs in the bike instead of the recommended CR8E plugs. http://ngksparkplugs.com/part_finder/motorcycles/step4.asp?id=5076&type=reg My bike only had 2500 miles on it when I bought it last years so I assumed the plugs had never been changed. I have 6000 miles on it now and the plugs really didn't need to be changed but I went ahead and put the CR8Es in. The CR7Es were black with carbon. "NGK Spark Plugs Heat Rating The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type." On the test ride afterwards it seems to have better pep but that might just be a placebo effect.