After the seizure (which I reckon happened long before I bought this bike), I decided to remove the engine and paint it. I’m going to split the crankcases and make sure all is ok inside. Going on what I found in the sump of the 51 year old C100 I suspect it’s full of old oil/tar/sludge, which has reduced it’s liquid oil capacity. New gaskets on order and seals all ready to be fitted. With the big bore kit too, it’ll be better than new. I’ve got all new cap head allen screws to go in the cases too.