i had a rusty tank on an OLD 76 honda cb 450f that i taught myself to ride on. it kept clogging the carbs it had gotten really bad. i went to my local bike shop and the guy who owns it said rusty tanks are common for older bikes. especially if the climate they have been in sucks. but he had some stuff that u put in the tank to fix it. it was two bottles . the first cleaned the tank the 2nd lined the tank with a rubber like material to prevent future rust. it cost me 30 dollars or so. but it fixed my issues. i cant remember what it was called. about the washers if they don't leak i wouldn't worry about them till the next time u mess with the tank.