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Scooter and Motorcycle AirBrush Painting – doing it the right way

February 11th, 2009 · 3 Comments

You got to a conclusion you want to do your own paint job – good for you! nothing makes you more proud of getting the job done right and by yourself!

But, there are a few problems and risks with painting a motorcycle or scooter:

1 – you don’t have more than one change of getting it right. Of course, you can let the paint dry and then start all over again but that’s not what we want.

2- unlike a car that has relatively strait and wide areas, motorcycle and scooter parts and surfaces are round and edgy, which makes painting them double as hard from the fact that they are more susceptible for paint drips.

The most difficult to handle paint, is probably the multiple coat or metallic colors that are usually done by spraying at least two different coats – the base color + the clear coat that gives the paint it’s shine.

In my vespa restoration, I used ford focus (that’s right) “electric orange” – it’s considered a 3 coat paint (but it’s actually 5 if you count the primer/sealer and the additional clear coat):

  1. primer/sealer
  2. white pearl
  3. orange
  4. clear coat
  5. another layer of clear coat

Although I consider myself as technical talented, this paint job was one of the hardest things in restoring the vespa scooter.
For start, not a lot of professional painters really wanted to get into this project, and if so, they gave a price quote high in the sky, way out of my budget.  One even accepted the job for a barter, but backed out the day after.
So, I had to do the job myself.

To get the best results, you have to have a sealed, air-filtered painting oven, which I don’t have…
Secondly,  although I have a steady hand, I can’t say that I use an air brush on a daily basis (not even yearly…but at least I have an air compressor). So, I built a shack covered from all sides but the door,  where I placed a fan. The fan job is to blow the excessive paint particles outside.

I bought a budget air brush, a Chinese brand that looked OK, a down-flow kind, that has the paint reservoir cup on top, while the paint flows down. The paint (Sikkens) was not cheap at all, in fact, just the paint part was 20% of the whole restoration cost!

You will need an electronic scale to make the mixing accurate.
You will have to mix clear coat with the hardener at 2:1 ratio (2 parts of clear coat + 1 part hardener). Once you mixed the clear coat with the hardener, you have only a few hours to use it.

Thin the clear coat mix with a thinner at about 10-30% (to a 100 cc of clear coat + hardener ADD 10-30 cc of thinner) . I used 10% thinner, but In retrospect I should have used more, maybe 15% thinning. I do not think that 30% thinning is practical for painting scooters, from the fact that the mix will be too thin for the body curves and edges, upping the risk of paint drips.
Ask the dealer you’re buying the paint from, for mixing instructions, hear what he has to say.

Anyway, do yourself a favor and don’t don’t use your “eye” to asses volume, buy an electronic scale and use it to accuratly mix what you need.

  1. PREPARING THE PARTS – get rid of all rust – use sand-blowing wisely. Why wisely? cause sand blowing is awesome, you blow-sand on a rusted area and slowly you see the rust being “eaten” by the sand, revealing new shiny metal. It is very tempting to over do it, but remember you are dealing with a thin metal sheet (if it’s a fuel tank or mud guard or vespa cowls) so use minimum sand-blowing as possible. Another advantage of sand blowing is that it can get into cracks and grooves which are impossible to reach with sand paper and hands. You can use liquid rust removers as well if necessary, this are good for light “dusty” rust that hasn’t yet penetrated deep. Just wet a cloth with some rust remover and clean the rusted area. If you have a few rusted metal bits, just put them in a small container with some rust remover. They will come out like new. Don’t forget to rinse them with plenty of water and spray paint them right away.
  2. get a smooth surface as you can with a good quality CAR KIT FILLER and a metal sheet as a spatula to apply it. Maybe there are plastic kinds as well.  For this job you have to  have two right hands. Apply as minimum filler as you can, and as accurate as you can. For sanding use a small, light eccentric sander. Start sanding with a coarse number 60 paper 0r 100. For smooth finish use at least 240 or higher.
    Don’t trust your eye, but use your fingers to feel the surface. Sometimes a scratch can be filled with very fine dust from all the sanding, so it is wise if you air blow or use a fine paint brush to clean  the surface and reveal imperfections if any exist.
  3. PAINTING – you must have light, and lots of it from different angles. Air brushing enemy # 3 (after #1: dust and #2: air brush gun not set correctly) is not enough light. Good and even lighting is extremely important, especially for the final clear coat.
  4. Airbrush the primer on all surfaces you want to paint, always use an automotive brand, not a home paint primer. Before you start on the scooter or motorcycle (or whatever), test the air brush pressure on a dispensable surface, like wood or an old chair. You want to learn the AIR BRUSH behavior.  Turn the air nozzles so the 2 air holes are horizontal, one on each side, that way you get a vertical spray shape ( | ), the best setting for LEFT TO RIGHT hand motions.There are two things you don’t want in painting: too much paint will result in dripping. the other bad option is orange peel or mat finish. Orange peel is a coating defect that occurs when the paint spray coming out of the spray gun, is not properly atomized. Mostly this happens due to low air pressure OR moving the spray gun too fast over the surface. Again, make a few tests before you paint the real thing.
  5. Water-sand the entire body and parts surfaces with a very fine abrasive water sheets (1000 to 1500 grain size) that you soaked in water at least a few minutes before use. use an 8 shape motion or back and forth on wide surfaces (whatever you feel comfortable with), and just back and forth motion on narrow areas, making sure you don’t sand the same area for too long. Always soak the sanding sheet in water from time to time – that will produce the best results.
  6. Let body and parts to completely dry. use air pressure to blow out trapped water in cracks etc’. let out in the sun for drying.
  7. Apply the first color coat. Let dry for at least 15-30 minutes (on a hot day 15 min are enough) until applying the next coat.
  8. apply the clear coat. The key word is a steady progress as well as keeping the air brush at the same distance from the surface as you progress. If you have lots of light, you can see exactly when a certain area is coated well, if you stay on it for even half a second more, dripping will occur. Always start spraying aiming to the side of the object (onto the open air) while slowly moving the spray on to the object. Stop spraying after a few cm away from the object (again, in the open air). That way, you make sure the beginning, middle, and the end of the spray trail, has the same amount of paint applied.
    Basically you paint overlapping rows/lines. Starting from the top, left to right (or RTL).
    If you have a wide area, you don’t stop pressing the airbrush after each row, but make sure you proceed to the next row only after your paint spray got out of the painted area. If you start a new row without going outside the just-painted area, there will be a short duration where you spray more at one area, risking a drip. Pay attention to edges, which are susceptible to dripping.
    If you do get a drip in the clear coat, just leave it for a later repair. Do not try to wipe it off, it will only smudge everything, making it unrepairable
    . If it drips on a part you can pick up, you can turn the part so the drip area is horizontal, that way the drip will stop from growing and maybe settle down (by gravity) to a point it’s unnoticeable OR easier to repair.
  9. after you are finished, let the fan work for a few more minutes and shut it off. Let the parts dry as they are for at least 24 hours. Do not move them out, or use the fan to speed up the drying process or the wet paint will catch dust, flies and other stuff that air brings. Note that even after 24 hours the paint is still very vulnerable.
  10. Remember that professional painters use ovens to bake the paint and dry it the same day. You don’t have an oven, so assemble the parts only after a week.
    Start working on repairs OR refinishing (if needed) only after a month
    . Be warned that being impatient and attempting to work on the paint after a few days only, will most likely result in cracking, smudging or ripping off the paint!.

Read my following article on orange peel paint defect repair.



Tags: Crafts · Motorcycles & Scooters


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