I just got a fuel tank from E-bay.. It was the 1973 CB500 Brown tank.. It had light to moderate rust on the inside..So I'm trying Simplyvalue Liguid bowl cleaner from Smart & Final.. Here in Los Angeles Cali....I'm doing a Half and Half with hot water..I also got a duster froma dallor store, so I can get inside to agitate...I'll let you know how it works, and I'll do a vid with my old tank...