Cam Idler Sprocket Question

Even though the cam chain guide sprockets for the 900/1000s and the 650s have different part numbers they are the same part and can be interchanged, there are some differences to the rear guide bracket though - more info here and here.

The 79 and later idler assembly is not going to fit an earlier bike as it is shaped wrong and is larger. You have to use it with a 79 or later valve cover. The earlier idler assembly will work on the later bike with no problem. (this is with respect to the 903/1015cc family. Liska makes good stuff and Z1Enterprises.com carries most all their line. Not sure where APE gets their idler stuff but I would also buy from them with confidence.