Saturday, June 30, 2012

Part 21 - Bodywork and Paint

It’s time to talk about bodywork. No, not the kind that involves plastic surgery. There’s a lot of bodywork preparation before you can slap the paint on. And slapping paint on is not really how it is done either.

The basic process:

  1. Eliminate all rust and old paint - sandblasting can do both. Surface should be about 80 grit and clean in order for the body filler to grip properly.
  2. Apply body filler to correct small surface defects and sand to 80 grit
  3. Clean the parts thoroughly. Use a degreaser/soapy water and follow with a cleaner like Eastwood Pre. Keep your hands off the surface - use gloves to avoid transferring oils from your fingers to the surface that will prevent paint adhesion.
  4. Apply epoxy primer (2 coats allowing for manufacturer recommended flash time between coats) and wet sand to 600 grit the day after application if needed. You can also proceed directly to paint if you laid the primer on nice and evenly.
  5. Apply top coat and wet sand starting at 1000 grit all the way to 2000 grit
  6. Use rubbing compound and then polishing compund. Use a buffer if you have one and know how to use it without causing damage to the paint.
  7. After 30 days of paint cure time, you can wax the surface.
  8. Sit back and enjoy the result (or call a pro to redo it).

What actually happens:
All rust and old paint from all the parts needs to be removed. Media blasting is an efficient way of doing this but make sure the person doing the blasting knows how to do it without distorting your sheet metal parts. I used Cost $225 to do the blasting. Block off all holes in your tanks properly or you’ll have blast media inside them which is difficult to get out. You could consider getting your parts powder coated at this point but that depends on how much bodywork you need to do. Powdercoat is recommended for the frame because of it’s durability. However, my frame had a lot of imperfections that needed fixing so I didn’t do powder coating.

After getting the parts back, I convinced myself I could still see signs of rust. Got Jasco Prep&Prime from Lowes and followed the instructions (or so I thought). What a disaster. After rinsing Jasco Prep&Prime off the tanks and frame I experienced flash rust. Things looked bad. I used a wire brush and sandpaper to clean everything up again. This was a painfully laborious process which negated the time saving benefits of having the parts blasted. I think I should re-read the instructions before using this particular product again. Rinsing with water is not the way to go. 

Flash rust

Many laborious hours of wire brushing and sanding

The gas tank had a ridge down the center with two concave depressions on either side roughly 1/8” deep.  Here's a short video showing surface prep and application of body filler.

The entire tank was covered with a thin layer of body filler and then sanded down with 80 grit wrapped around a flexible block. This generates a ton of dust so was mostly done outdoors with a sanding face mask.
First of many body filler applications

First of many sanding sessions

This process was repeated many many many times until the surface was perfect. The number of hours that went into the tank makes it most likely the most expensive tank in creation. Fortunately my garage time is free.  The rear fender required some work on the sides to cover up the weld distortion from mounting the internal struts, and to mold in the fabricated taillight extension. The front fender required some minor work too. The oil tank was in bad shape and required a complete coating of body filler and a lot of time sanding. Many hours were lost in preparing the oil tank. The handlebars needed work to mold the gauge cup and panel modifications.  

Frame molding

Rear Fender

3/8 brake line welded in place to protect wiring

Oil Tank

Sanding the oil tank 

Swingarm molding
After bodywork, it was time for paint. To protect everything from paint spray and dust, I erected an 8x8 pop-up tent inside the garage and covered this in plastic. WARNING: Vapor build up inside the tent can reach a level at which the slightest spark can cause an explosion. You have to ensure adequate ventilation and use an explosion proof fan. This is a dangerous way to paint due to the high solvent content. Do not try this at home.

Two eye bolts were screwed into the ceiling to suspend the frame inside the paint booth.  Parts were thoroughly cleaned with soapy water and then wiped down with Eastwood Pre. It is critical to keep your fingers off the parts – you do not want to transfer oils from your fingers to the metal as the oils will prevent the paint from adhering properly. Use a tack cloth to remove any last minute dust fibers that may have settled on your parts. Some tack cloths leave behind a sticky residue so be careful with product selection. If you can remove the dust fibers with an air gun, you will be better off.

In the "booth" ready for primer

The primer is a 2 part epoxy primer/sealer from I used a $15 harbor freight spray gun with a disposable moisture/particulate filter to shoot the primer. The compressor was a borrowed 25 gallon Craftsman unit. I had no prior experience spray painting with a compressor. There is plenty of painting advice on the web and you can get a good insight into the process by reading Joann Bortles book.

Disposable Inline Moisture/Particulate Filter

Harbor Freight Spray Gun

To cut a long story short, the primer came out ok. Always use a mask or respirator, disposable paint coveralls, gloves and safety glasses. There will be a lot of particulate in the air - you don't want it settling on your skin or getting into your eyes and lungs.

Primed Parts

The Eastwood Epoxy Primer was ready to sand after being left overnight and can be topcoated up to 5 days without sanding. The primer was wet sanded with 600 grit to eliminate orange peel and other imperfections. In some places I accidently sanded directly through to the metal so had to clean and reprime sections. This is painful and something you want to avoid by being very careful around the edges.

Primed and wetsanded

Final paint was a single stage automotive urethane from I figured that Single Stage Urethane would be more straightforward to apply than a 2 stage basecoat-clearcoat system for a first time painter. I screwed this up multiple times. Everything got painted at least twice and some things like the tanks.... 3 to 5 times.... Fortunately I bought a gallon of paint.
Bouelvard Black Single Stage Urethane

Painting is a very dusty and messy process.

Paint dust clings to everything
Mask - clean filter and filter after painting

After screwing up the paint application and sanding through to primer accidently a number of times, I resorted to painting outside. Setting up the tent again and managing all the paint dust inside the garage wasn't something I was terribly keen on. Airborne particulate was obviously more of a problem in the open air, and an insect or two landed on wet paint. Insects should be removed immediately so that the paint can flow around the affected site. Nothing a final wet sanding can’t take care of. I ended up with a lot of orange peel. You can probably see it in the handlebars:

A little bit of orange peel

I tried spraying a guide coat of white rattle can paint over the urethane - this allows you to make sure you sand everything down to the same level surface, eliminating high and low spots in the paint. A light misting is all you need. While wet sanding you want to wet often to remove the sanding paste that results. I kept a hose nearby for repeatedly hosing down the parts. Unfortunately I got a lot of water into the tank because the gas cap leaked. This resulted in surface rust on the inside of the tank which had to be treated.

Block wet sanding the guide coat with 1000 grit
After wet sanding down to 2000 grit (1000, 1500, 2000), rubbing compound was used to remove the fine scratches left behind by the 2000 grit paper, followed by a finer polishing compund to remove the marks left by the rubbing compound. There is nothing quick and easy about this process. It takes time and will test your patience. 

Rubbing compound and polishing compound

You should be rewarded by a glossy smooth surface if you do everything right. If you didn't, you will have to grade your work on a scale of 1 to 10 where the number is the distance from the part that the paint looks good. For example, a 10 means the part only looks good from 10 feet away, and a 1 means the part looks good from 1 ft away. My parts ended up being about 2ft parts. I eventually redid the tank completely.....

After urethane topcoat, wet sanding to 2000 grit and Turtle Polish

Frame after top coat, wet sanding, rubbing compound and polish

Some things I didn’t know that I wish I had:

  • Make sure your paint surfaces are scrupulously clean.
  • Figure out your spray gun settings on scrap material. This is trial and error - many videos on have good pointers on spraygun adjustment. I ended up spraying at about 50psi measured at the gun with about a 4 inch fan at about 8 inches away and paint control full open.  

  • Paint settles on the part you are trying to paint and overspray settles on parts in the vicinity. This overspray causes problems because the paint that settles on distant surfaces is relatively dry and causes a rough texture. On a frame this can cause problems if you add a coat to the backbone  and don’t follow through to the lower rails. Paint the backbone first and then proceed to the lower rails so that you can paint over the overspray to keep everything smooth. If you respray the top you need to respray the bottom...
  • Make sure your parts are spread far enough apart in your spray booth and be conscious of where you are directing your spray. You don't want overspray on other parts in the booth or you’ll leave the rough overspray texture on them.
  • Be careful when you spray the underside of fenders or the gas tank tunnel. The paint shoots back out at you as fast as it leaves the gun. Stand to the side or you’ll get a face full of paint. Fortunately I had safety glasses and dust mask on when this happened...
  • If you notice a paint run, leave it. You can correct this after the paint has cured. I had limited success correcting runs in wet paint.
  • Make sure you leave adequate flash time and you spray at the correct temperature specified for the activator and reducer. Failure to do so can result in solvent pops that will require the paint to be stripped and redone. Hundreds of little pinholes will suddenly open up in the paint after an hour or two. Unfortunately they go through all paint layers.
  • Do not let the paint gun run out of paint. What is left in the gun will start gelling while you are mixing a fresh batch of paint and come out in chunks when you least expect it wrecking your paint job. If you do get chunks, wait for the paint to dry and then repair.
  • Don’t stress too much trying to get perfect coverage on the first coat. Second and third coats will even coverage out. For the single stage urethane paint, a mist coat for the first layer can help to prevent runs and sags by giving the second layer something to grab on to.
  • Avoid excessive orange peel. This is hell to sand out later. Can be caused by moving the gun to fast, being too far from the surface etc. Google “paint orange peel”
  • Avoid runs and sags. Caused by excessive paint, gun too close or moving too slowly.
  • Remember it is only paint. It can be sanded off and redone. Ad infinitum.
  • Don't use a coiled air hose from the compressor to the paint gun. The coils catch on everything. Use a straight line for the spray gun and keep one hand on the line to prevent it from touching freshly painted parts.
  • Make sure your gas tank and oil tank caps don't leak. You don't want water getting into your tank and starting rust while wet sanding.
  • If you are going to seal your tank, do this BEFORE you paint - the sealer sticks like crazy to everything and will make a mess of your paint.
  • Good luck.

How to use a paint cup.