The Mower Drive Belt can be replaced by the steps as outlined in the section headed Attaching the Mower. The Spindle Drive Belt is replaced by removing the slot head capscrews that hold the belt cover to the mower housing, release the Spring on the Idler Pulley
Bracket and remove the belt from the Arbor Pulleys. To reconnect, put the belt around the pulleys (Figure "K"), connect the Spring back to the Idler Pulley Bracket and around the Spring Post, replace Belt Cover and secure into place with the slot head capscrews.
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Source: Owner's Manual, B-207, B-207E, B-208, B-208S, TM-7072/I-70, Rev. 3-70, courtesy of J.C. Stahl