odometer zeroed after new battery

My early Rocket did something similar when I disconnected the battery to install my Gerbing's/Battery Tender hookup. The bike had 2900 miles on it when I disconnected the battery and 900 when I hooked it back up. Then for an added twist, when the ODO should have turned over to 1,000 miles, it turned over 10,000! Went through 2 more speedo's under warranty, but their trip meters wouldn't reset. Finally just put the original back on when I found it sitting in a box in the back of the old Cycle Mart. The mileage read high, but at least it functioned.
 
If the odo resets to 0 again, you should have it looked at by the dealer before you run into some serious "odometer tampering" laws in Texas.
 
Disconnected the battery again and reconnected, the odometer retained its mileage information.
I am thinking that there may have been a wierd electrical spike that hit the unit and caused the reset. There were a few times that there may have been loose connections on the + side while trying to re-route the cables to fit the new Odessy battery posts.
 
Drag that red cable along the post a few times and get it to spark.