Yep, sounds like the speedo.
NST has the same problem, that is, the right hand drive activates on inserting the link and settles after a second or 2. I had to do the same thing Jamie suggested, just lift the wheels off the ground until it settles.

In the rush of the build its not something i sent any time fixing or investigating but i think it was the speed controller (sabertooth). I'm currious to know if other people using the 10 amp model have the same problem (or don't) and will stand corrected but IMO Its not a fault on the speedo as such, just poor design of the circuitry.
Tiberius on the other hand never glitches, as the programming in the Wotty speed controller cleverly designs out this issue.