The gas tank is one of the most visual parts of your bike, especially on a chopper, in fact, on classic cruisers, the gas tank is one of the only places you can put graphics. Imagery can certainly define the entire character of your bike, so painting your gas tank is very important. You can do this in a few simple steps, and the more care you put into it, the better your tank (and your bike) will look.
Empty the tank of gas.
Remove the gas tank from the frame. There are usually a few screws in the front and in back. In addition, there may be bolts under the tank. Either way, you will know when they are all off. Before you can do this, you will probably also want to remove the seat, and disconnect the fuel shut off valve, as well as the tank's fuel line.
Remove the gas cap from the tank. If yours is not budging, you may decide to leave it on to save time and reduce the chance of breaking the tank seal or cap. If so, tape this part off very carefully right now. Make sure there are no fumes, or excess gas in the tank. Dry it completely.
Rig up your sand blaster and blast away all the paint on your gas tank. Go right down to the bare metal, but don't push your luck. You don't want to compromise the tank metal at all. In fact, on old gas tanks, and if you suspect cracks, or rust, you may just want to hand sand, or use a lower power sanding disk attached to a power drill.
Inspect the tank for cracks or weaknesses, especially around the seams and dents. If you find problems you have to take care of these now. Take it to a professional to repair or use an approved epoxy to fill the cracks and weakness along with a fibreglass layer. Because, again, the tank is a highlight of most motorcycles, taking the tank to a professional might be the best option.
Apply your first coat of primer. Use fast strokes to create several light layers. Let the tank dry between coats and use several coats until you are satisfied. You can apply as many primer coats as you like, sometimes as many as six or more can be used.
Sand your primer using a very high-grit sandpaper such as 120 or even 360 grit. This sanding is to smooth the natural texture of the paint, and allow your next coat to go on as smooth as skin. You will want to apply one coat, let dry, then turn the piece over and hit the other side.
Tape off any areas you do not want to be covered, if any, then change or clean your spray gun nozzle and fill your paint sprayer with your final paint coat. Holding your nozzle several inches away from a test sheet (aluminium or similar, a piece of poster board even works), spray a few test strokes, moving the nozzle at different speeds and checking to see the result. There should be no bead-ups, or runs in your strokes, but the area should be completely covered in one or two strokes.
Apply your paint to the gas can using the nozzle and stroke you mastered on the practice or test sheet. Apply paint to the whole surface at once, getting the top and sides done first. Then after drying, the bottom side. Get into all the crevices around the welds, using a smaller nozzle to avoid runs and bead-ups.
Apply the metallic flake, or top coat to the gas can if any. Follow the same process as you did with the first coat of paint.
Use paint made especially for the type of metal your tank is made of. Rust proof metal paint for autos or bikes is a good choice. You can buy it in several colours, and finishes, like flat, gloss or matt. The higher quality you can afford, the better.