Your videos are always well presented. Calm, thorough and with good explanations. For us airheaders and would-be tinkerers, boxer2valve and your collection is the only good sources of video-inspiration that I know of. Looking though the uploads, you didn't visit the inside of the crankcase, looked at bearings, the cylinder studs .. ?
Dave, The '76 models have the duplex (double row) chain without the master link, so you have to use a bolt cutter to remove them. The replacement chain I use has a master link. You can order one from Euro MotoElectrics, part# TChain258 and the replacement crankshaft timing sprocket has dual teeth, EME part# TimingSprocket198. The procedure is the same. Here is a document on how I did this for a 1977 RS. brook.reams.me/bmw-motorcycle-rebuilds/1977-bmw-r100rs-rebuild-project-index/11-bmw-1977-r100rs-replace-timing-chain-crankshaft-timing-gear-nose-bearing/