I believe the VIN number is a seven digit number on the frame but I can't research it because all the search engines need a longer number. I think I need to decode it? I have no paperwork for this bike. My grandfather left it to me and it's been sitting in the garage for 30 years. Last registered in 1975. The battery still gets a spark, key turns. I need a new air filter. I want to get it registered in my name but I need the VIN number. I have no idea where to start. What would you do?