That's correct Steve, my cuz, when he owned a bike repair shop , would clean his tanks with phosphoric acid, (the acid they use in Coca Cola) thoroughly dry them, then pour a cup full (about 250 ml) of two stroke oil in them, and top up with fuel. the bikes (both 2 and 4 stroke) would smoke a bit until that tankful of fuel was consumed, but it was worth it, as the problem rarely came back.
As you mentioned in your post, the burned fuel/oil mix coats the mufflers internals, and prevents (or at least slows down) rusting. A good idea if you're going to invest in a NOS exhaust, they cost more than the bikes did new! Cheers, Terry.
