On my 97 F3 i have spotting on the swingarm behind the rear sets and i tried a wet cloth at first then i tried washing off with soap and that still has not worked so before i get into heavier stuff i figured i would ask and see what is recommened to help out with these stubbon spots. they are not rust it just seems the previous owner kinda neglected the bike for awhile.

Any suggestions???

 

You could maybe try some spray on rim cleaner....I am not sure if that would work but it might be worth a try. (just don't leave it on too long)