When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
There is supposed to be a hole in the tensioner assembly where a 5mm Allen (hex) wrench "keeper" can be inserted to hold the tensioner pulley in its retracted position (after retracting it fully with a wrench as shown in the attached left drawing). This provides enhanced user safety and leaves both hands free to replace the belt. To remove the "keeper" after installing the new belt, retract the pulley an additional slight amount, pull out the Allen wrench with pliers, then allow the tensioner pulley to gradually return to its applied position.