Common Mistakes when Painting a Motorcycle & How to Avoid (or Fix) Them.
Article by Benny at Custom Motorcycles Inc.
Some people can dismantle an engine and put it back together in no time at all. Some can ride like a professional. And yet, these types of people still avoid doing their own paint jobs, even when using high-quality professional motorcycle paint. Why? Maybe because they don’t have the patients to put the time in, a fear of not mixing the materials properly, or not knowing the adequate prep work.
There are many things that can go wrong when giving your bike a new paint job, luckily for you, they are all avoidable and fixable. Here is VMR’s own list of common painting mistakes and how you can avoid them.
Cracking includes random sized cracks, splits, or wrinkles appear in the paintwork and often resemble, in both texture and appearance, a reptile’s skin.
Insufficient preparation: The first step in avoiding cracks (or any other imperfections) is to prepare the surface correctly. Cracking on the surface itself should be removed before applying new paint
Lifting of substrate: If the incorrect reducer is used in the topcoat, or when certain materials are top coated before a full cure, the undercoat can lift in a way similar to cracking.
Incorrect reducer or hardener: Its important to follow the paint manufacturer’s guidance on which reducers and hardeners to use with each paint. Low-quality products can often lead to adverse effects on the paint.
Incorrect mixing ratio: If the mixing ratio between hardener and paint it can cause cracking and other adverse effects to the dried paint.
Environmental conditions: Too much heat or humidity during the application and curing processes can cause surface damage, such as cracking.
Excess: Praying too much paint on too quickly can often lead to cracking.
How to Fix It
Start by allowing the paint to cure completely. Once cured, the cracking and any other imperfections can be sanded out and a new coat of paint can be applied. The best advice is to avoid cracking by considering the common causes mentioned above.
Orange peel is one of the most common mishaps encountered by people who paint their own motorcycle. As the name suggests, this imperfection is when the dry paint looks and feels like an orange peel.
Excess: Most imperfections can be caused by too much material in full wet coats, and orange peel is no different, as it prevents the paint from forming an even film before drying.
Improper use of reducer: Using the wrong reducer can cause solvents to evaporate too fast, this makes the paint film dry before the material has properly reached its final desired look. Ensure to use the correct reducer for the temperature and conditions under which you are working.
Gun troubles: Ensure to use the correct spray gun, tip, and air cap when applying the paint. Insufficient air pressure can prevent the paint from atomizing correctly too, and therefore, preventing it from flowing out into the wanted finish.
Poor technique: Anything from the position of the gun tip to the degree of overlap between passes can cause orange peel. Practice your technique first.
How to Fix It
If the orange peel is minimal, you can sand it out with fine grit sandpaper, then compound and polish to restore its finish. If the damage is severe, sand out all imperfections and repaint with the correct reducer material, air pressure, and technique.
Runs and Sags
Runs and sags don’t only happen when painting our motorcycles, it also happens when painting kitchen cabinets. Here’s why it happens
Improper reducer/too much reducer: Choosing the right reducer and hardener is essential to achieving the finish you want. Choose the correct ones for the paint you are using and check the conditions of your shop, as reducer that evaporates too slow and excessive use of reducer are the most common culprits for runs and sags.
Excessive film thickness: Excess material in wet coats will lead to running paint.
Insufficient flash time: Not giving the solvent enough time to flash during the first coat and before applying the second coat causes runs.
Inadequate air pressure: Insufficient air pressure at the tip of the paint gun also causes sags. Using the correct fluid tip and air cap are just as important as using the proper gun for a specific paint.
Poor technique: Improper technique can cause all kinds of defects. Make sure to practice on a different surface before painting your bike.
How to Fix It
If the paint is still wet, you can remove it with a solvent, clean the area and reapply. If the paint is dry, you’ll need to sand out the runs and reapply paint.
Fisheyes are small, circular craters spread over the paint film. They are such a common problem you can even find special Fisheye Eliminator products.
There is only one reason for the appearance of fisheyes in your paint job:
Contamination: Which can be found on the substrate and is the main cause for fisheyes. It happens during the application or prep process and it is when water and oil enter the air stream due to the absence of water and oil separator, or the reuse of shop rags, which will have dirt from other materials. Ensure to use clean rags and take care when using other products near the painting area.
How to Fix It
If the paint is still wet, you can remove it with a solvent and then reapply. If its dry, sand out the fisheyes and repaint. Add fisheye eliminator products too and ensure the correct preparation of the surface.
Flaking and Peeling
Flaking and peeling are generally a bad sign. It happens because of delamination, meaning the dry paint film is no longer adhering to the substrate.
Improper surface preparation: Any imperfection on the surface area can cause delamination. The finish of your bike will only be as good as what lies underneath the final coat.
Insufficient film thickness: It is important to have a consistent and adequate paint thickness. If applied to thinly, it will eventually pull away from the surface.
Failure to follow application instructions: If specific application instructions are not followed, such as certain fully cured undercoats must be sanded before applying a topcoat, it can lead to peeling and flaking.
How to Fix It
If the surface area is small, you can simply remove the flaking paint and reapply paint as you would for a spot repair. If the area is larger, then you will need to sand the entire area and repaint. Make sure to follow instructions carefully.
If you paint is dry and yet, the substrate is showing through, you have poor hiding.
Too much reducer: Reducers are transparent, thus too much of it will take away from the hiding capacities of the paint.
Wrong primer color: Color primers are harder to cover, depending on the color of paint you are using. Use light-colored primers for light-colored paints and darker primers for darker colors.
Uneven color on substrate: Variations in substrate color, such as body fillers, can cause poor hiding.
Insufficient coats: Manufacturer’s advice doesn’t always achieve the correct level of hiding and more coats are needed.
Improper paint prep: Ensure the paint is properly agitated before applying. This is especially true for older paints, as pigments may settle to the bottom of the container.
How to Fix It
All you need to do is to continue applying proper agitated coats of paint until you achieve the desired level of hiding.
Now you know what the most common painting mistakes are and how to avoid and/or fix them, you can begin respraying your motorcycle with total confidence. Remember to practice on an off-cut or test surface before applying any paint or primer to your bike.