A belt tensioner (14) for a power transmission belt (12) is provided that operates on an endless path and that utilizes asymmetrical motion control. The belt tensioner (14) has an arm (18) with a belt engaging section (22) and a drum section (26), a support member (16) for securing the tensioner relative to the belt (12), whereby the arm (18) pivots about the support member (16), and a tension spring (20) that urges the arm (18) to pivot about the support member (16) in a first direction and urges the belt engaging section (22) against the belt (12) with a force to tension the belt. The tensioner (14) also has a stator (28) inside the drum section (26) utilized to form arcuate spaces (30) circumferentially spaced around the stator (28) between the stator and the drum section (26) and arcuate shaped wedges (32) in the arcuate spaces (30).
