DIY Home-painting with Spray Touch-up for Partial Frame Rusting

Rust is an inevitable part of any old or out-of-print motorcycle that has been around for a long time. Some people think that rust is a part of the motorcycle's character, but from an objective point of view, it can make the motorcycle look old. However, there are still parts of the motorcycle that are still alive and it would be a shame to paint them all. In such a case, it is worthwhile to try to repair the parts using spray paint.

Thinking that a full restoration or full paint job can be done at any time.

We wanted to give the motorcycle as much of a "used motorcycle" look as possible, so we used partial paint instead of a shiny repaint.

The battery case inside the side cover is rusted due to the electrolyte. The part where the paint film is peeled off and the base is in the state of red rust is a repainting point because it gives a feeling of shabby.

Owning and riding an out-of-print motorcycle that was manufactured decades ago is one of the most maniacal parts of the motorcycle hobby. It was a long time ago, and now people have their own way of enjoying old and out-of-print motorcycles. The condition of the engine and the brake is maintained and repaired, and the plating and the paint of the exterior parts are kept in the state of wear and tear, and the number of users who enjoy it is increasing.

A certain level of fading or deterioration is called "vintage" and is highly valued. For example, the fading of the gasoline tank of the candy paint is the deterioration of the color clear by the ultraviolet rays if it is judged only from the quality aspect.

Stripping or sandblasting the old paint off and repainting it with modern high-performance paints will give a far better finish than the original paint quality. But in doing so, the original, which has survived for decades, is lost in an instant.

However, there is a question of degree even if it is said that natural deterioration is accepted. The standard is different for each person, but if the aging is regarded as a motorcycle's own age, it will be saved, but if it gives a shabby impression, it is regrettable.

Wrinkles and blemishes on our skin are a sign of age, but rust on steel parts can make a motorcycle look ragged. In particular, the deterioration of the black painted parts of the frame and undercarriage can have a major impact on the overall look of the motorcycle. On the other hand, if the exterior parts such as the petrol tank and wings are a bit worn, the motorcycle will still look good if the black paint on the frame is in good condition.

If that's the case, it's only natural that you'd want to paint the entire frame. In fact, a motorcycle finished that way will look instantly rejuvenated. However, if you want to go one step further, you can choose a partial painting of the frame. Even professionals don't like to do partial repairs on red or blue colored parts, but with a black frame, even if the color is a little off, it's often not a problem.

From a professional painter's point of view, it would be better to repaint the whole thing than to repair a small part like a motorcycle frame, even though it would be less work and give a better finish. That's certainly the way to go, but if, for example, only 20% of the total painted surface is rust that spoils the look, it's an interesting choice to keep the remaining 80% of the original paint from decades ago.

Here we are repairing the rust on the pressed frame of a Yamaha 90cc motorcycle that was manufactured over 50 years ago by partial painting. Many people may feel that it is a trivial job to paint only the rusted parts after having made the frame itself. However, except for the rust on the engine mount and swingarm pivot, the original Yamaha black texture is still intact, so we chose to do a partial repair because we didn't want to mess with it.

However, while the trump card of a full paint job can always be used, a partial paint job to improve the appearance is a more effective repair technique than you might think.

If you want a natural finish, spray rather than a brush

Unlike big motorcycles, small-displacement motorcycles with pressed frames are easy to take down the engine. After removing the frame, degrease it with kerosene. When the coating of oil and grease is removed, the rust of the base becomes apparent.

When it comes to partial repair, touch-up by brushing comes to mind, but spray paint is definitely more advantageous when it comes to creating a natural look and feel. When the paint film peels off due to scratches or rust, there will be more or less bumps with the surrounding area. As experienced painters will know, it is not easy to fill in the gaps in the paint film with touch-up paint applied with a brush or brush. In addition, since this is a rust repair of the lower part of the frame, the painting area will be quite large, so when you paint with a brush, you will have to worry about the brush marks.

When spraying, the painted area will be wider than with a brush or brushstroke, but this makes it easier to blend in with the original paint. This is the same logic behind painting a wide area from the door panel to the fender to repair a partial dent in the door in sheet metal painting of automobiles.

On both pipe frames and pressed frames, rust is most noticeable around the swingarm pivot, but the round cross section of the pipe frame makes it harder to see the roughness of the paint technique when spraying than on pressed frames. Don't try to apply a thick coat all at once, but apply a thin layer from a distance for a more natural finish than you think!

However, even if partial painting is considered easy and trivial, it is important to follow the basics of painting if you want the painted area to look natural and as clean as possible.

Masking and degreasing cleaning is important for both full and partial painting.

If you sandblast the paint and rust off and repaint it, the quality will be good, but it will ruin the atmosphere of the original. Therefore, the rust removal and papering of the old painted surface is kept to a minimum.

The rust is removed to expose the bare steel, and the paper is applied without removing the old paint. Black has a high hiding power, so if it is painted over well, the base metal will not show through.

If the paint is not degreased properly, it will bounce back, so don't start out with a thick coat. Here we are using a spray gun, but the procedure is the same for canned urethane spray paint. The boundary between the original paint and the new paint is not clearly divided, but if it is painted so that it may give a gradation, it will be finished without a sense of discomfort.

Whether it's a plastic model or a motorcycle, the quality of the paint will vary greatly depending on the finish of the base coat. Naturally, it is essential to degrease and clean the painted surface. Particularly, when painting areas such as engine mounts and swingarm pivot areas that are covered with oil and grease, careful degreasing is necessary.

However, if you want to paint with engine and foot parts, you should use kerosene or oil wash to dissolve the oil and then degrease with parts cleaner. Of course, the frame should be cleaned with kerosene. In the case of press frames, the engine mount and swing arm pivot are box-shaped, so removing them has the advantage of removing the dirt inside the frame.

Once cleaning is complete, the damaged paint is prepped. The rust tends to occur on the battery case and the lower part of the frame, so use #400-600 sandpaper to remove the rust and expose the underlying steel plate. At the same time, you can apply the sandpaper to the other parts you want to paint, but this time you don't need to use the surfacer or primer to expose the base because you can use only black paint for painting.

In the case of partial painting, it is usual to do masking when separating the painted part from the rest, but since it is a frame alone, it can be done roughly there, too. When painting with the engine and the foot area attached to the frame, masking other than the painted part is done with newspaper. At this time, by keeping the space between the frame and the newspaper as far apart as possible, you can avoid the sprayed paint from bouncing off the masking and reattaching to the paint film.

Also, do not try to apply a thick coat of paint at once, either on the frame itself or on the bodywork, but apply a small amount of paint in thin layers. If you find that the paint bounces due to poor degreasing, you can easily redo it if you find it in the thin paint stage. A thin layer of paint also has the advantage of making it difficult to see the difference between the unpainted and painted areas.

Touch-up painting has an image of being a temporary fix. To put it bluntly, the partial paint job described here is also a lazy job. If you sandblast off all the old paint and powder coat it, the shine and strength of the paint film will be incomparably better than partial painting.

However, even with the partial painting done by the procedure introduced here, there is no reoccurrence of rust even 5 years after the repair. And by choosing the partial painting, we were able to keep the original 50 years old paint on the rear fender part that stands out with the pressed frame.

If you think that you can always do a full restoration to make it shine all over the body, you can actively choose an easy partial painting to hide the rust and rags that you are worried about.

I was able to paint not shiny and smooth, but a thin film of paint as only small displacement motorcycle. If you paint too much, the difference from the original surface will be noticeable, so it's better to paint a little less.

When the paint is completely cured, polish the whole with wax with compound and blend it with unpainted parts. When the original paint film has deteriorated to the point that it does not shine even with compound, it is better to deal with the whole painting instead of partial painting.

The top of the rear fender is still painted as it was 50 years ago, but by painting the battery case and the rear of the engine, the entire frame was tightened up and the tired look was removed. We recommend painting parts of the frame to give it a natural aged look.