I have a 1985 lowrider with 3.5 fat bob tanks. It has the small speedometer and a separate tach which is stock. It has the speedometer gear on the front wheel. I'm looking to convert to to the single large speedometer. How do I know if I need a 2.1 or a 1.1? Any help and links would be great. I found some good buys on Ebay but I'm not sure if they will work. THX Dan

I think I would raise the bike and turn the front wheel one turn while measuring how many turns the cable end makes.:s