I baught an 82 Goldwing this year and have been working on modification and restoration. It only had 12k miles on it but had sat out in the weather for decades. pretty cruddy. Fuel tank is my latest project, it was completely rustin inside, its under the seat so did not remove tank. decided to clean in place. filled with water with dishwashing liquid in it and then rinsed it our after a couple of days, got most of the heavy loose rust out. Then filled with Evapo-Rust and let is sit for about 36 hours. This stuff works exactly as it is advertised. It is sold under several different names, the original manufacturer does not market it but licenses to others. It actually disolves the rust instead of coating it as ospho does. It isnt an acid, does not do anything to the actual metal or other coatings, only attacks oxide. I got a 5g bucket from Northern Tools for about 80.00. Its reusable so it has lots of further use and has good value.