Nessism

I don't exactly know. Used a couple gallons of deck wash in a large garbage can. Soaked some motorcycle exhaust pipes. Took a long time to remove the rust so the concentration couldn't have been too high, plus the raw steel turned green.

I've used oxalic acid to remove surface rust from an old bike for my neighbor. Stuff worked a treat. It's the right product for that application. If you have heavier rust, and raw steel, oxalic acid isn't as good as other materials. Phosphoric acid is much better, but you should keep it away from paint. I've used phosphoric acid to clean rusty motorcycle gas tanks and it eats off the rust in just a few hours. For the bike in question, I'd use the Evaporust. Best stuff available, but not the cheapest.