Gear Ratio Spreadsheet
Thanks to Mtbierio (Cugino Pegaso)

The Spreadsheet, in Excel Format, can also be downloaded from here: Gearing Spreadsheet.

Q. Is there any way of checking the Speedo Accuracy, using the Tach (Rev Counter)
A. Sure. See the Speedo Spreadsheet.

Q: Are there any Other Gear Calculators.?
A: Sure. See Harl#380 found this:

The Direct Download is:

Download GearCalc v3.012  for Windows (19K) (Shareware)

and the Bike Library (Doesn't currently contain the F650)