Prepping Your Motorcycle Paint Project
The first thing you need is a place to do this work if you are doing more than a small paint repair. You can paint just about anywhere, but there are certain things you need to do if you want to achieve a good paint job on your motorcycle.
First, you need to get an area closed off with some plastic sheeting. You can make a small “paint room” in a garage or shop, but you are going to want to make sure you have every seam sealed with tape, because if paint can escape, it will. You will also want an oscillating fan. One with variable speeds. You will want to get your lighting squared away so that you can see what you are doing. You can get some regular old clamp lights and pay for some LED bulbs if you want to get a really bright paint setup for cheap. Here is a pretty great site about turning your garage into a booth if you want to get really serious about it.
You can repaint over an existing coat, whether it’s on a frame or a tank. If the paint is in good condition, you can simply scuff it up with 400 grit wet-and-dry paper and paint over it. You might be taking a risk with compatibility with the original paint, so test the existing paint first. Hold a rag soaked in general purpose thinners on the paint—if the thinners dissolves the existing paint, consider stripping it off. It is usually a better idea to always strip the tank, but does add to the cost. Strip and clean disks can make this part of the job easier, but pay attention to your surface. It can be easy to get carried away and start removing the surface with these
Filler is only necessary if your tank needs some significant buildup from things like dings, dents, or if there is any rust damage. If you are working with a new tank, you can skip ahead to the next part of the guide. Get some automotive body filler, usually a 2-part product that you mix together to use. Once mixed, the reaction causes the mix to harden and cure the filler. Always follow the warnings, and definitely wear gloves with this stuff. Grab a clean rag and some wax and grease remover and wipe down the tank thoroughly before moving on.
Once you are done cleaning the tank, find something solid to mix the filler on/in. Absorbent materials like paper, cardboard, and even wood can actually absorb the resins that make the filler effective, so find something like a cheap plastic cutting board, or even just a busted piece of plastic if as long as it is big enough to mix the filler on. The best way to get the job done right is to follow the instructions on the filler itself - they all work pretty much the same, but those instructions are always going to give you the best results. Some of them give you really strange mix ratio instructions, so try to find one that is as straightforward as possible. Also, you don’t want to overdo it when you are mixing this stuff up because it can set pretty fast, so mix smaller Spreading the filler is more of an art than a science. It is somewhere between putting frosting on a cake and mud on drywall. You don’t want to go more than ⅛” thick with the filler, so if you do have any dings in the tank you will want to layer on the filler and build it up over multiple coats once each one is dry. One of the things that will save you the most effort (sanding) down the road with this is trying not to leave any mounds of filler as you go. It can be quite the task because just about every surface you are working on has some kind of curve to it and your eyes can start playing some serious tricks on you when you get really focused.
Here is a quick video from 3M on using body filler: