You should change them once a year..but I haven't mine runs so well, and last time I pulled them out they still looked great. Same NGK plugs from November 2003 with about 15,000 miles on them.
If it runs great and the plugs are still in excellent shape why mess with it I guess.Gas Man said:I normally agree SV...but the real question is "Do we have to?"
I know a few guys that haven't changed theirs and their bikes are like 4 years old with 10K on em...