Hi James,
I have had similar problems. On most bikes that have a computer when you disconnect things like the speedo and some other electrical parts you will need to reset the computer. I am not sure what the dealer has to do but I would go to the dealer and ask him to reset your computer or clear it. Although it was not a Harley I pulled the gas tank off my Triumph and the computer needed to be reset, same thing with my Buell, pulled a module from the electrical system and then needed to reset the fuel injection system. I would bet that something needs to be reset or cleared especially a speedo. They don't want you to disconnect them and rack up miles on your bike.
Hope this helps!
Ride Safe
Lenny