PaintTank

When you begin the project of painting your tank, you need to start by being honest about your goals for the project. Do you want a professional-quality paint job, or are you just covering bare metal to keep it from rusting or looking like junk? Are you somewhere in between? Your goals will determine largely how much work is required and what result you can expect. This wiki will cover the two extremes.

Both Options

Drain the gas as much as possible. Turn off the tank petcock and remove the tank. Remove any decals and the residual adhesive. It's easiest to remove the adhesive with a citrus solvent like "Goo Gone" and then follow up by removing the citrus solvent with something a bit more aggressive like acetone. Note: depending on what kind of paint exists on the tank, acetone may very well damage the existing paint.

Take the gas cap off (open cap, remove the 3 or 4 real bolts, ignoring the 4 fake bolts).

Close the tank petcock and remove the fuel hoses. Finish removing the tank. Remove the tank bracket from the tank (you may paint that part separately).

Ensure all gas is gone from the tank. You may have to let it sit for several days in a well-ventilated area like the great outdoors with the fuel lid off in order for the residual fuel to evaporate out. The tank needs to be dry. Once the tank is dry of all fuel, you can mask the fuel inlet and the petcock and vent tube with masking tape to prevent paint from getting inside the tank or especially inside the petcock. Alternately you can completely remove the petcock so you don't inadvertently damage it while painting.

Note, this document assumes you are using "rattle can" paint you can buy at a home improvement or big box store, and not specialized "pro" automotive urethane enamels that you buy from a paint jobber and spray from an HVLP gun in a booth. If you have access to the materials and tools to do a pro catalyzed finish then you don't need this wiki.

Gather some materials you will need no matter which course of action you are going to take:

3M/Scotch blue masking tape, 3/4"
Primer of choice, one 11oz "rattle" can

For primer, an acrylic enamel or epoxy primer is highly recommended. Unless you are taking the entire tank down to bare metal, a lacquer-based primer (such as Rustoleum, Duplicolor, etc.) is not recommended, since it may adversely react with underlying paint.

Paint of choice, one or two 11oz "rattle" cans, and potentially clear if you intend to use clear

For top-coat, acrylic enamel is highly recommended, such as Rustoleum's acrylic enamel "automotive" paint. Duplicolor (lacquer) is not recommended and ordinary Rustoleum (alkyd enamel) is also not recommended, for different reasons, both affecting durability.

400-grit wet and dry sandpaper
Red Scotch-brite pad (NOT green!)
spray bottle
dish detergent
mineral spirits
a roll of blue paper shop towels
a length of stiff wire (coat hanger)

A few things to remember:

Any imperfection in the surface will show through to the next coats. So if you have a flaw in the surface and you prime over it, you will have a flaw in the primer. If you have a flaw in the primer and you paint over it, you will have a flaw in the paint. You can't prevent this. Whatever step you are on, get it perfect before moving on. Flaws will not go away as more paint is applied.
Once you discover a mistake or flaw, stop and go back to prep, after letting whatever you are doing dry completely.
Paint is influenced heavily by temperature and humidity. Choose your time and place to paint wisely. If you have to wait for summer, wait for summer. You'll be glad you did.
Paint dries by allowing "volatiles" to evaporate out of the paint leaving behind only "solids". The thicker the paint, the longer it takes to dry because the volatiles have to make their way out of a thicker layer of solids. This is also why it's critical to not mix paint chemistry. For example, painting a fast-drying polyurethane enamel over recently-painted acrylic enamel will effectively seal the volatiles in the acrylic and cause the acrylic to never cure and stay soft forever. Or spraying lacquer on top of an enamel may cause the volatiles in the lacquer to dissolve into the enamel below and cause cracking or lifting of the paint. And remember, until these volatiles are fully gone from the paint, it's not truly dry. This can take a long time. The paint is fragile until then.
As paint dries it shrinks, revealing scratches, dings, and other imperfections over time. Make it perfect when you can.
Rattle can paint won't stick to glossy or overly slick surfaces. You need to scuff it. The reason you can re-coat in a few minutes is because the new coat of paint effectively joins chemically with the one below it, but once a coat dries you will have to scuff it to give the next coat a "tooth" to stick to.

Option A : re-paint to not look like junk

This option assumes you are not doing any bodywork or clean-up of the tank, and you don't care about the quality of the eventual finish, just as long as it's durable and it covers any bare metal. You can cut a lot of corners when doing a paint job like this.

Wet-sand the entire tank using 400-grit wet-and-dry sandpaper. Use a spray bottle of water with a few drops of dish detergent to spray on the sandpaper and on the tank where you are sanding. Completely sand the entire tank. Any areas where there is exposed metal or rust, sand down to the bare metal and ensure all rust is removed. Every place that will be painted must be sanded with 400-grit. Once you are finished sanding, clean the tank with clean water and wipe it down with shop towels.

After it is cleaned and dried and you are certain it has all been sanded, you can go over it again with the red Scotch-brite pad to even out the sanding scratches from the 400-grit. One you finish scuffing with the Scotch-brite pad, use a blue paper shop towel moistened with mineral spirits to thoroughly clean the tank of all sanding dust.

To paint, put the mounting screws back through the bracket bolt holes on the bottom of the tank and fashion a hook from coat hanger or other heavy/stiff wire wrapped around the screws so you can hang the tank in a position where you can paint all sides. Hang it from a tree, your garage ceiling, or however you see fit.

Now spray the primer according to the instructions on the can. Spray the first coat lightly where you get 50-70% coverage and then follow with a second coat ensuring you have 100% coverage over any bare metal, waiting a few minutes or whatever the instructions suggest. If you have a significant amount of bare metal to cover, a third coat may be a good idea.

One note on spray can technique: the most likely place you will get a run or drip is at the beginning or end of your "stroke", when you first depress the nozzle. To avoid this, start the "stroke" outside of the tank and then smoothly move the spray pattern over the tank and past it before you let up.

Let the primer dry. Many half-decent spray-paint jobs are ruined by over-eagerness to touch it after painting. Even if the can says it's dry in 10 minutes - leave it overnight, preferably in a warm, dry place.

Once the primer is fully dry, scuff/smooth it with the red Scotch-brite pad. This should remove any dust bumps or roughness to the paint surface and provide a good "tooth" for the top coat.

Repeat the paint with the top coat in the same manner as you painted the primer. Put at least one coat after the first full-coverage coat. So if you painted one light 50% coverage coat, then you need two more coats at a minimum. More coats is not a bad idea. Keep adding coats until you run out of paint.

Now you seriously need to let this paint dry. Rattle can paint can take days or weeks to fully cure, even if it is dry enough to handle. You might reassemble the motorcycle and easily dent or chip the paint for a month after it was first painted. The more coats you painted, the longer it will take to thoroughly cure. It is best to let it dry outdoors in the sun in 60-90 degree F temperatures with <70% humidity for several days before handling it.

Option B : You want it to look pro

There are certain things that lead to a really pro looking paint job, even if you are using a rattle can: 1. condition of the part you are painting 2. surface prep 3. painting technique and paint selection 4. commitment to doing it right

In addition to the materials listed above, you will need a few more things:

1000 and 2000 grit wet-and-dry sandpaper
a foam/sponge sanding block like a 3M number 20 sponge saanding pad
cutting or rubbing compound (Turtle Wax rubbing compound works) OR 3000-grit sandpaper like 3M Trizact
final polishing compound like Meguiars Ultimate
some soft cotton rags (old T-shirt)
a microfiber buffing cloth

First, deal with the condition of the part. If there are dents you don't want to live with forever, pull them out. You can pull out a lot of dents with a hot-glue type dent puller like you can get from Harbor Freight. Once you get the dents pulled out so it is as straight as you can get it, then you might have to consider whether you are going to do any filler. If so, then you will need to sand out the paint where you are putting filler so you can fill directly on the bare metal using 220-grit paper, then apply the filler according to the manufacturer's instructions. If you are in this rabbit hole, you'll be here a while, or otherwise you are wasting time reading this wiki.

Once the tank is straight and smooth so you are ready to paint, you need to prep it, much like for the quick & dirty paint job above. Wet-sand the entire tank using 400-grit wet-and-dry sandpaper on the foam sanding pad. Use a spray bottle of water with a few drops of dish detergent to spray on the sandpaper and on the tank where you are sanding. Completely sand the entire tank. Any areas where there is exposed metal or rust, sand down to the bare metal and ensure all rust os removed. Every place that will be painted must be sanded with 400-grit, and always use the foam sanding pad. Once you are finished sanding, clean the tank with clean water and wipe it down with shop towels.

Paint selection is critical if you are going to get a pro quality finish. For rattle can paint, to get a durable finish with no or minimal orange peel you will need to use an acrylic enamel for both primer and top coat. If you want to use clear, use exactly the same paint. Ideally you get all of this paint from the same vendor. I recently did a tank with Rustoleum Acrylic Enamel and it turned out beautifully, but I have also used Krylon Fusion in the past with great success. However, whichever paint you choose you will need to practice with it to learn to paint without orange peel and how heavy of a coat you can apply without getting runs and drips.

If you have any exposed metal then you can spot-prime over the exposed metal. After the primer has fully cured, maybe 24 hours, wet-sand the spot primed with 400-grit, being very careful to "feather" the edges of the primer with the preexisting paint, otherwise you will be able to see these paint edges in the final finish. Follow up with red Scotch-brite.

Once the tank is thoroughly sanded and primed where necessary, clean it with soap and water, dry, and then scuff it thoroughly with a red Scotch-brite pad. Then clean with a blue paper shop towel moistened with mineral spirits to remove all sanding dust. Be thorough. Anything left on the surface, like adhesive residue or dirt or oil or old gas will prevent the new paint from sticking.

If it is not perfect, now is the time to make it perfect. Sand (400 grit), prime, sand/feather, clean, scotch-brite, mineral spirits. Repeat this process until it's perfect. Then you will be ready to paint.

Hang the tank as described above from the tank bracket bolts. Paint according to the manufacturer's instructions on the can, but note the following:

Numerous "light" coats, that is light coverage, or what pro painters call a "dust coat", will result in excessive orange peel. The paint has to flow out to avoid orange peel. You need to put as heavy a coat as you can without getting any drips, so practice painting with your choice of paint on some other smooth sheet metal surface (like a trash can) until you know how heavy you can paint without drips, and paint like 80% that heavy. The heavier the coat, the less orange peel, but it's all for naught if you get a drip or a run. You have to find the happy medium.

The instructions for paint, if you use the Rustoleum Acrylic Enamel like was suggested, will say to recoat within minutes or after 24 hours. What they are not telling you is that if you need to apply extra coats, you will need to scuff it again with the red Scotch-brite and the finish will not be hard enough to prevent balling up when you try to scuff it for at least 24 hours. So you should put as many coats as you can a few minutes apart, until you run out of paint, and then DO NOT TOUCH IT FOR AT LEAST 24 HOURS. The paint will be delicate after 24 hours but you can handle it. It will chip and ding easily. After about a week, you can move on to the next step. Do so quicker at your own peril. It's very easy to get in too much of a hurry and screw up what would have been a perfectly good paint job. Wait. Time is your friend.

After you have painted at least 3-4 full coverage coats and let it dry for at least a few days, better a week, then you can assess the orange peel situation and know what you need to do to move on.

If you are going to spray clear over the color coat, then at this point you will need to scuff the color with your red Scotch-brite pad and then spray several coats of clear in the same manner as you did the color. Then wait a few days or a week and continue with orange peel remediation.

If you have heavy orange peel, then you will need to start wet sanding using your foam pad and 1000 grit paper, lightly and without much pressure. Be especially careful around ridges and corners since it's very, very easy to sand through the paint in those spots and then you have to repaint the entire thing. Go slowly and check your work by drying the tank where you just sanded and look for shiny spots, which indicate low spots that have not yet been sanded. Continue to 2000 grit once you have a uniform matte finish.

If the orange peel is minimal, then you can start with 2000 grit wet sanding. If you are continuing from 1000 grit, then you are just taking out 1000 grit scratches if you sanded out the peel with 1000 grit, so a complete but light sanding is all that's needed. If you are taking down some orange peel then you will need to do more deliberate and thorough sanding with 2000 grit and your spray bottle using the foam block. Once you have completed the entire tank with 2000 grit, you can move on to either 3000 grit or rubbing compound. If you use rubbing compound, then you need to again be very careful since you can easily burn through the new paint with too much pressure with an abrasive cutting compound. So tread lightly and go slowly.

If you used rubbing compound then the tank will be shiny after you are finished, but it's not polished and ready. With 3000 grit it will be uniformly matte and will require polish. Move on to buffing with the final polishing compound and microfiber polishing cloth. If everything goes perfectly you'll have a show-quality finish when you are done.

Wait at least a month before you wax the new paint or apply any decals or masking tape.

After you paint

Take all the masking tape off and put the petcock back in. Put the fuel cap back on with anti-seize on the threads. If you have tank rubber protector, then put it back on. Put the petcock back in if you removed it. Now you can put the tank back on the motorcycle.

If you have to do any masking for any reason on the freshly painted tank, wait at least a week before putting tape on it (better a month). The adhesive in masking tape can react with new paint and cause it to show a tape line even after you remove the tape.

After about a week or a month, measure and put new tank decals on if you prefer. It's best to wait as long as possible, up to a month, before putting a decal on since you may have to remove it if it is not straight and you might lift the paint if it is not absolutely fully cured. Also if you have to remove a decal, you may have to clean up adhesive with a solvent, which would be bad for the fresh paint until it is fully cured.

Avoid overfilling the tank or dripping gasoline / petrol on it when you first fill it up. The paint may still be susceptible to solvents for some time. Park in the sun for the next month to aid curing.