I see a lot of people talking about back firing. Some talk about adjusting this and that, some removing pair valve. Does back firing hurt anything? I have a 04 vol and it has back fired since day one. I thought this was normal, since this is my first motorcycle. It really don't bother me, but if is going to do some damage maybe I need to have this looked at. It has just had its 4000 mile service done, no problems. Any information would be great.