There is no tensioner as such, the gearbox on these machines pivot around the axle and are kept tight to the belt by a spring somewhere around the back of the gearbox (good luck finding it) You can check if its there by trying to turn the box forward (to make belt slack) if you feel spring pressure then that bit is ok, as long as the belt is in the box pulley and on the engine pulley and its still slack, then you need a new belt.
Paul, March 2010
