In the Feb. issue of Classic Bike, there's an article on using Castrol R. It explains how if you want to switch after using caster bean based oil to another oil, you must tear down the engine and clean it or run the engine with a flushing oil before switching. It stated that there was info on this on www.castrol.com, but I couldn't find anything. Does anyone know what kind of "flushing" oil should be used?