Posted November 8th, 2021 at 12:53 pm by Dan Musick
The old Allister and Allstar openers use two black sprockets. The one above the motorhead moves to activate the limit switches as the limit dogs reach their shut-off points.
The one above the door acts as an idler. Raynor used similar black sprockets just for idlers above the door.
Over the years the chains stretch, loosen and as a result, the pitch of the chain breaks the teeth on the sprocket. To prevent this problem, Allstar replaced the black sprockets with black pulleys.
In 2021 Allstar quit selling parts for their openers, and now we carry a white idler pulley that has a similar shape as the black pulley. The outside diameter is 2 1/2″ and the bolt hole for securing the pulley to the end bracket is 1/2 inch. These don’t break when the chain loosens.
If the sprocket above the motorhead breaks, you will need to get a new opener. Those sprockets are no longer available.