How to Bring Back the Luster of the Fuel Tank Using Ultra-fine Sandpaper?

00-2-1.jpg How to

It is not uncommon to find that a motorcycle that has been regularly cared for will maintain its beauty over the years, but it is not uncommon to skip washing and waxing the motorcycle and before you know it, the painted surface is rough and crusty. If waxing doesn't bring back the luster, you might want to take the plunge and use sandpaper, which will give you results beyond your imagination.

Paper can only be used if there is a clear coating.

02-2.jpg I don't know what kind of condition it was stored in, but the fuel tank of Honda CB750F has no glossy and crusty clear paint even though it has not been scratched or tampered with in detail. I would be tempted to repaint it if the top coat of paint was obviously damaged, but the two-tone of navy blue and white and the condition of the HONDA logo mark are not bad, so it is annoying on the contrary.

 

Rain, wind, and ultraviolet rays are great enemies for the paint of a motorcycle and a car. There are many examples of motorcycles and cars that have been treated with love and affection when they were new, but after a year of standing around, they are still wet from the rain and dust from the sand.

The paint on these poor motorcycles deteriorates really quickly. The first thing that happens is that the surface loses its smoothness and rainwater marks are left as water spots, and from there the scuffing progresses further. Waxing or polishing with a compound can restore the shine and luster, but if you don't take care of it, the condition will deteriorate further.

The fuel tank of HONDA CB750F shown here is one such example. I don't know how long it has not been washed, but it is so crusty that it looks as if someone has harassed it and scratched it. If it had any noticeable scratches or major dents, I'd be more than happy to replace it with a slightly better-used fuel tank, but unfortunately, it's not in bad basic condition, so it's a bad idea.

There is a pattern of paint deterioration in the form of fading of the clear color of the candy paint, which is common in out-of-print models from the late 1960s to the 1970s, and this is sometimes prized as a natural appearance. However, it is a pity that the paint surface is crumbling due to lack of care, which is different from such weathering over the years.

If you want to improve the appearance of such a fuel tank as much as possible, there is a means of polishing the clear layer. This is only possible on fuel tanks that have a clear coating on top of the colored topcoat. In the case of this CB, if there is a clear coat of paint on top of the dark blue or white paint, and the crusty deterioration is confined to the clear coat, polishing is possible.

On the other hand, this method cannot be used for old motorcycles that do not have a clear coating or low priced small-displacement motorcycle because the paint color itself will be degraded by polishing. If you polish an inconspicuous area with a compound with high polishing power and the paint color is transferred to the rag, it can be judged that there is no clear layer or the clear layer has deteriorated remarkably.

 
POINT
  • Point 1: Ultraviolet rays and rainwater damage the paint, so surface protection by washing, waxing and coating is effective.
  • Point 2: When polishing deteriorated paint, it is important to keep it within the clear layer.

Sandpaper doesn't cut below the clear layer.

03-2.jpgIf you use coarse paper, the scratches will become deeper, so use a very fine paper for finishing. If the chalking is too severe to be removed with the ultra-fine paper, gradually make the paper coarser. The key to clear coat polishing is to use as fine a grit as possible, rather than coarse to fine.

05-2.jpg Although ultra-fine paper is difficult to clog, polish with water. To polish a flat surface evenly, it is effective to attach a plate to the back of the paper, but corners should be polished gently with your fingers.

06-2.jpg The lack of shine is the same as before the work, but you can see that the shine has been evened out by applying the paper. The effect of the compound is improved by sharpening the painted surface once.

 

One of the conditions that can cause clear paint to lose its luster and become crusty is a condition called chalking. This is the result of ultraviolet rays and moisture destroying the molecules in the paint and causing them to turn to powder. When you scrape the surface of a guardrail or fence on the street, you may notice a white powdery paint on the surface, which is another example of paint chalking.

In the case of this CB, even if you rub the fuel tank surface with your finger, the powdered clear coating will not stick, so it can be concluded that it has not reached the stage of chalking. In such a case, it is expected to recover the clear coating by polishing. However, it is important to keep the amount of polishing to a minimum because it does not mean repainting.

If you scratch deeply with coarse sandpaper, you may scrape off the topcoat layer beyond the clear layer. The more you polish, the more you will remove the top coat color, which is completely counterproductive. When sanding with paper, it is necessary to keep it within the clear layer.

Specifically, at the first polishing stage, use the finest paper you can find to polish the clear coating. In this case, I started with 1600. As stated on the product packaging, 1600 is a super-finish level of fineness and has very low scraping ability. Depending on the degree of chalking or scratching, the scratches may not disappear at all.

However, I would like you to be cautious enough to see how it goes. As a result, there might be a case that 1600 is too fine and you need to coarse up to 1000 to get the effect. Even so, it is safer to start with a fine-grit paper in order not to overwhelm the clear layer that has been damaged in any way.

Since it is hard to clog the paper with weak grinding power, it is hard to make a big difference in sharpness between air and water polishing. If the color of the topcoat is mixed in the grinding water, it means that the clear layer has been penetrated and it is better not to push further.

The overall polishing process will result in a shiny finish that is different from a chalked or scratched condition. After that, you can change to No. 3000 sandpaper and continue polishing, but aside from making the custom paint mirror finish, if the purpose is to improve the crusty paint film, there may be no visible effect even if you proceed to No. 3000. Nevertheless, by applying No. 3000 sandpaper, you can lower the mountain of unevenness polished by No. 1600. This will certainly make the next polishing with compound easier.

 

POINT
  • Point 1: Coarse sandpaper penetrates deeply into the clear layer, so use fine sandpaper even if the grinding power is low.

Polisher can be used to remove fine scratches

07-2b.jpg SAKAE GIKEN Hanasaka G is a universal chemical that has three effects of cleaning, polishing and waxing in one bottle, reflecting the developer's own experiences and wishes. It can polish not only metal and resin painted surface but also clear cowl screen.

08-1.jpg Since it has been polished with ultra-fine paper, just a light polish with a compound will bring out the gloss of the clear coating. If you rub Hanasaka G with hard cloth, there is a risk of increasing small scratches, so it is better to use a microfiber cloth that is soft to the touch.

09-1.jpg When wiped off with a surface that does not have Hanasaka G ingredients on it, the gloss is restored from the matted state. Applying only wax without paper polishing will not bring out such a depth of gloss.

 

The clear coating polished with No. 3000 sandpaper will have a uniform glossy finish as if it were covered with tracing paper. Even though it is the same glossy finish, it doesn't have the crusty feeling before the work. This is when the wax with compound finally comes into play.

The compound for polishing and the wax for surface finishing are two different products, but you can use Eiken's Hanasaka G Wax, which has three functions of cleaner, polisher, and wax, to remove the paper marks and make the surface shiny. Spread Hanasaka G on a soft microfiber rag and polish by rubbing. It is important to polish with force, because just stroking the surface will not give you the best polishing power.

In addition, in order to efficiently remove the paper grain, you can also use an electric polisher. If you can prepare a special product with a strong motor torque is ideal, but if you polish the fuel tank for motorcycles, which unlike automotive sheet metal, the size of the parts is small, you can combine a small diameter pad with a rechargeable drill driver to polish several times more powerful than hand polishing.

Polishing pads are made of different materials such as wool and sponge, and each has a different grinding power. In general, wool pads have more grinding power than sponge pads, so if you want to use a sponge pad after finishing paper, choose a sponge pad, or an ultra-fine pad if available.

After polishing, the clear paint was restored from the matted state to the glossy state as if it was sprayed with water. This gloss is the effect of smoothing out the small scratches on the surface of the clear paint, not the result of applying a thick coat of wax. If you look closely, you can still see streaks in the clear paint, but the difference from before is obvious. If you feel that the gloss has become dull even after waxing, you may be able to improve the situation by preparing the surface with ultra-fine paper and then polishing with a compound.

10-1.jpg If you have an electric polisher, you can polish deeply in a shorter time than hand polishing. By utilizing the torque of the motor and the weight of the motor itself, the heat of the polishing area is increased and the polishing power of Hanasaka G is improved.

11-1.jpg If the polisher is pressed too hard on a particular spot, it may heat up and burn the paint, so polish while moving the pad.

12.jpg When I remove the masking tape to compare before and after work, the dark blue color looks deeper in the front that I prepared from the base and polished. If it recovers to this level, I think I can continue to use it without repainting for a while.

POINT
  • Point 1: The compound is effective even if you polish it by hand, but the work efficiency is improved by using electric tools.
  • Point 2: When erasing the polishing marks of ultra-fine paper, use a sponge pad for ultra-fine particles instead of a wool polishing pad.
 

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