It really depends on how much time and expense you want to put into it.
The easiest and cheapest way is to drain it and pour a gallon of plain white vinegar in there and swash it around. Let it set for an hour or so and repeat the swashing/shaking and have a look. If the rust is gone then you have to drain and flush the vinegar out. Some folks put in a couple of tablespoons of Baking Soda in the flush water to neutralize the acid. Then rinse it a few times. Now is the tricky part. You have to drain and dry it before it flash rusts again. You can get it as dry as you can by draining then immediately fill it with gasoline and about a 1/2 can of Heet. Change the fuel filter and off you go. The Heet is there to absorb whatever water is left in there.
One tip is to remove the petcock to aid in draining.
The other option is to just fill it with gas and put a new fuel filter on it and ride it. You may find the rust is gone in a day of riding and the filter will pick it up.
Others will suggest you do a complete drain, clean and lining the tank. And that will work but it is expensive and in my experience that would be a last resort only on a heavily rusted tank.
Don't fix it until it's broken.
John
83 KZ550M1
83 KZ1100LTD
Also own:
2010 Harley Ultra Classic Limited, 2008 Harley low rider 71 CB350/sidecar
