The proper tensioning is as follows (note that you can also
refer to your Owner's Manual):
Find the adjustment nut on the threaded rod
underneath the drive unit. It is on the bow (front) side of
the drive unit.
Loosen the retaining screw and turn the nut
clockwise a turn or two. This should loosen the nut.
Turn the adjustment nut counter clockwise until
it just starts to feel tight (This is the proper adjustment for
belt tensioning; increased tightening of the nut will over-
tension the belt and ultimately cause problems.).
Tighten the thumb set screw - this does not
need to be over-tightened either as it only has to keep the
nut from turning.