My friend has a z440 that the lower chain case bearing destroyed itself. Took it apart yesterday. Besides putting two new bearings in can you explain how the tensioner works. Has the two plastic riders separated by a spring. There is a plug on the front but there is not adjustment. I’m just not sure if it broke when the bearing let loose and the chain came off. Also on the cover there is a pad mounted on the inside with 4 Phillips screw and something was mounted on that pad that is now broke off. Chain looks good. The gears look good too so my plan is to replace both upper and lower bearing and what ever is on the cover that broke off.