Abstract: A lock for motorcycles, bicycles and the like which have in their driving mechanism a sprocket and chain. Principal parts of the improved lock include a pair of straps which are strong and rigid, preferably made of steel or other strong material. One of the straps extends upwardly behind the chain, then forwardly and then downwardly in front of the chain. The other strap has a flange in front of the first strap then turns forwardly below the chain and then turns upwardly behind the downwardly turned portion of the first strap. A pin is secured to the bottom of the enclosure. The lower portions of the straps have holes which register when the lock is closed and through which the arm of a padlock may be passed.