Race Bike Painting

When I got fed up with paying people 200 plus to paint my bike, only to trash the new paintwork at the next meeting, I decided to take up spraying myself. After some desultory results, I had a look on the web for some hints and tips on spraying. I couldn't find much at all, so just carried on and learned myself. So here is...

The Bodger's Guide to Paint Spraying

Why bodger's guide? Well, the techniques here are NOT designed for show-quality paintwork on a carefully restored classic. That takes a great deal of skill, time and patience. Racers generally don't have much of any of these commodities, so we'll just go for something that looks reasonably good from a distance - say a few feet away.

First of all - a hint to first-time racers: Don't bother. Paintwork is a lot of effort and/or expense, you probably don't have any sponsors to impress (if you do, try to get them to pay for a paint job), and you're only going to crash at your first meeting anyway. If you bought the bike with race bodywork fitted, leave it as-is. If you've bought new bodywork, leave it white. Some carefully selected stickers or stripes of gaffa tape can liven it up suitably.

Also note that some companies will sell you bodywork with a pre-coloured top coat ("gel-coat"). This saves a LOT of effort, and is well worth it for the little extra it costs (typically 20% or so). Unfortunately I find the people who do this (ARD come to mind) never stock the right fairings for my bikes.

A note: measures used in this guide are generally litres. If you're American - forced to use an antiquated system of measurement - just remember that a litre is roughly a quart, that "colour" is the proper spelling of "color" and that "hot tea" is a stupid description. Tea is ALWAYS hot - the revolting beverage marketed by Snapple is not worthy of the name.

Tools of the Trade

It's possible to get reasonably good results with cans of spray paint from Halfords. Much of what follows applies to them too. But I'm going to assume you've got access to the proper equipment - since I have, therefore it's easier for me to write as though you do too. One note, though, if you do buy aerosol cans of paint, buy the biggest ones you can. You will get through a lot, and it's considrably cheaper in the larger size cans. So the full list is:
  • Compressor. Almost anything with a resevoir should be OK. The bigger resevors (50 litres or larger) just mean the compressor won't be pumping too much of the time. But a cheap 25L one will be fine. Make sure it DOESN'T have a tool oiler in line, but you don't necessarily need an "oil free" type.
  • Spraygun. The very cheap ones supplied by Machine Mart as part of their six-piece air tool set are rubbish. Mine wasn't expensive though - it came from Costco as part of a two-gun set for 30 quid or so.
  • Blow Gun. You know, the simple air-blasting tool for the compressor which basically consists of a nozzle and a trigger. Used for drying wet items and removing dust, loose dirt etc.
  • Cellulose Paint. Find a car paint supplier in the Yellow Pages (I go to "the Car Paint Company" in Hayes, West London). They will sell three types of paint: Two Pack, Cellulose, and Poly. Two Pack is best, but unless you have an remote air-fed breathing mask, or don't mind being slightly dead from cynanide poisoning, forget it. I honestly don't know what "poly" is, but that leaves cellulose as our basic race bike paint. You will need undercoat - sometimes described as "filler-undercoat", and the actual colour(s) you want to use. You can generally pick from a variety of standard colours, plus many car colours. Undercoat comes in grey, beige and maybe some other colours - pick whatever works best for your top colours.
  • Cellulose Thinners. Available in 5L cans. It's largely toluene and hence has a secondary use as an llegal fuel additive to boost your octane levels. Comes in "standard" and "high gloss". The high gloss version takes longer to dry and therefore gives a better finish for top coats.
  • Wet & Dry Abrasive Paper. Get a variety of grades. I find 600 grade most useful, but would suggest getting 400, 600, 800 and 1000 grade.
  • Lint-Free Cloth. "Lint-free" meaning something that won't leave bits of fluff all over your paintwork. Best thing I've found is the "reusable" kitchen roll sold by Sainsbury's for about 1.50 a roll. "Mutton cloth" is often recommended, but you have to cut that up, and I find it leaves loose threads around.
  • Mask. It's tempting not to bother for quick jobs. But look at a filter after using it, and imagine that lot in your lungs. A decent rubber mask with replacable filters is a LOT more effective than the crappy disposable paper masks, but they're better than nothing.
  • Eye Protection. Obviously, you've got this already, since you're not even supposed to use a screwdriver or spanner without it... If not, splash out a couple of quid on a pair of plastic glasses or goggles. I wear plastic-lensed glasses already, so just rely on them.
  • Surgical Gloves. A box of these for under a tenner (perhaps as little as four quid) will save you going to work the next day with Kawasaki Green fingernails.
  • A Spray Area. Perhaps the most difficult requirement of all. Remember this simple fact: EVERYTHING IN YOUR SPRAY AREA WILL GET COVERED WITH PAINT DUST. It's reasonably easy to remove, but if you're using your garage, move your father's classic Norton and your girlfriend's 748 outside first. Cover anything else with old sheets as much as possible. The area directly behind where you're spraying will catch overspray - make sure it's covered well with newspaper, or you don't mind it being painted. You can't really spray outdoors, unless it's a VERY still day, as all kinds of crap will get blown onto your wet paintwork.

Preparation

The experts will tell you that paintwork is about preparation, preparation and preparation. Yeah yeah. We'll ignore two of them and go for a quick job. First of all, it's MUCH easier to paint new bodywork than it is to repaint stuff that's already been fitted.

What you must do is take the shine off the new bodywork. This "keys" the surface to accept the paint - otherwise it'll just fall straight off. Rub it down with wet 600 grade paper until it's no longer shiney. At the same time you can remove the worst surface imperfections - using 400 grade if necessary for better abrasion. Any bad scratches (fairing been rattling around in the back of a suppliers van for a while?) should be removed as they'll definitely show through. Any cracks (this is NEW, right, how come it's cracked already?) should be repaired with a fibreglass repair kit.

Now wash the bodywork down to remove the abraded dust. I find the easiest way to do this is to put it in the garden and hose it down. Leave it to dry. For a quicker job, wipe it down with a cloth soaked in white spirit (from a DIY store), and blow it dry with your compressors air-gun.

Undercoat

First stir the undercoat thoroughly, then mix it with 40% thinners. This is easiest in a large clear glass jar, as you can easily estimate the 60-40 split. Or just pour the paint into your spray gun resevoir, stick a screwdriver into it, guess where 2/3rds more would be, mark the screwdriver with a blob of paint and top up with thinners to that point. Stir well.

Your task - should you choose to accept it - is to get as much undercoat on as possible in the shortest time. Ignore people who tell you that you need lots of thin coats. Four thick coats is my usual technique. That's one layer, followed by another as soon as the first is dry (10 - 15 minutes). Then leave it at least an hour, sand it down and apply another two coats. Again, leave at least an hour and sand down ready for the top-coat.

When applying the paint - undercoat or topcoat - you want the surface to look wet. Spray in "sweeps", starting from off the side of the item, sweeping over it and off the other side. Sprayguns can generally be set to give a vertical pattern, which you use in horizontal sweeps, or a horizontal pattern, used in vertical sweeps. The sweep should be slow enough that a thick glossy layer is layed down, but not so slow that the paint runs. You can of course go over it again to add more paint, but I find it better to use a couple of slow sweeps rather than several thin ones. The idea is to get it as heavy as possible without it running - which you can obviously only tell by experience. If it does run (by which I mean the paint pools into a "sag" or drip, then don't panic - you can fix that at the next sand-down. If it was supposed to be the final layer then you're probably going to have to do another.

Sanding down can be done with 400 grade paper for the undercoat, and 600 or 800 grade for topcoats. You'll notice when you first start rubbing that the surface feels rough, but this very soon disappears as you rub it (using a circular motion). If you rub right through the paint coat, either your paint wasn't thick enough or you're being too vigorous. Use the wet-and-dry paper wet, and hose the bodywork down afterwards, or clean it off with clean rags and plenty of water. Leave to dry, then blow off any remaining water, dust and/or dead flys with your blow gun before the next coat. To save time, you can use the wet-and-dry dry, and clean off the dust with white spirit - which can be very quickly dried with the blow gun. You will get through much more wet-and-dry this way, though, since it will clog up very fast without water.

Top Coats

This is actually very similar to undercoat, except that you need to be more careful about runs, as the paint is not so gelatinous. I find that a couple of quick coats (leaving 10-15 minutes between each) followed by a rub down, followed by another two coats is usually sufficient. More coats will give a stronger finish (though two-stroke weight fanatics should note they'll add more weight!)

The last top coat is the most critical. You're not going to be rubbing this down at all, so make sure there's no dust or anything else that will show through.

When you're done, you can if you choose rub down with very fine grade paper (1000 or 1200) and then finish off with "rubbing compound" - available from the guys who sold you the paint in the first place. I find the benefits are minimal, but it will give you a slightly better shine at the cost of lots of extra work.


I just received these comments from Tom Benford, who races in Powerbikes with Bemsee and works in crash repairing cars. It's nice to see that an expert doesn't think my article is complete rubbish - and he adds a few very useful notes.

I just read your bike painting guide which is great. I have a couple of suggestions though. There is a better way to remove the residue left when you have flatted the primer: Let it dry, then use a scotchbrite pad to loosen the dust and blow it off with a blowjet. It's faster and leaves a cleaner surface to paint on. Then wipe with a takrag and it's really clean. For even more convenience you can dry sand the primer with frecut 400 grit and just blow it off then paint straight away. We dont use cellulose, but to get a good finish on the final coat try doubling the amount of thinners. Watch out for runs!

The poly paint you refer to is usually called synthetic and is good for vans or anything of large area but would not be appropriate for bikes. As we all know,this is all a colossal waste of time as a crash is never far away. Dont look for nice paint on my bike!

Finally,those cheap paper masks should not be used for anything other than protection against dust.

Regards, Tom.

Thanks for those comments, Tom.


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