#41 is the same width and roller separation just not as tall(and they come in 10' roll, thats 2 chains) .... but i had the stock tensioner on and was working fine. I bought one of them clutch cover spring tension, but the extra space the bolts made after putting it on made my peddle hit the bolt (found out after i took out a few links to make it fit right). So after replacing my original carppy one it would never say tight and the pulley loosened and dropped it to the bottom ... if you take a sharpie marker after re-adjusting and circle the washer you will know if it moved down.... or just google, or go on youtube, and look up "DIY Chain Tensioner (Motorized Bicycle)" for a cheep safe tensioner