Hey,
Quote:
Could it be that it is working properly, however, since it's on the stand there is no load (hence no vacumn) on the motor?

Sort of, but lack of vacuum is not the issue methinks.
Did you hear the RPM's increase for just a second when you engaged the cruise, then suddenly drop off as it disengaged?
Probably the same reason that it shuts off when the clutch is pulled in while cruising at speed....the unit is designed to cancel when sensing a too-high accelleration rate. With no load on the rear tire while on the centerstand, the cruise "brain" treated it just like wheelspin or a disengaged clutch.

Pfft, safety devices........:p
Shane