I recently purchased a 1971 CB350. I was told that the bike has not been started in 7 years. I opened up the gas tank and saw that gas has been sitting (for those 7 years I´m assuming) and there was rust forming at the bottom of the tank (I couldn´t tell if it had significantly eaten through the metal or if it was minor). Either way, what is the best (and cheapest) way to refurbish/salvage the tank? Thanks.