every how often to change spark plugs

one hundred thousand miles Roy

They are easy to change I would change them at 60,ooo miles although Honda say 105ooo miles.

As of 1996, all newer vehicles have an OBD II onboard diagnostic system which will let you know when their life has dropped more then 50%. If your vehicle is having a hard time starting, bucking or chugging, it may be time to replace them. Otherwise, you should follow the maintenance schedule recommended by Honda or even earlier!