At first, painting a motorcycle engine may seem like an intimidating DIY project, but with a little time and effort, anyone can learn to do a decent spray-can paint job. You can take great pride in doing it yourself and saving money at the same time. Granted, there are some limitations to doing the spray-can job (colour options, finish options, etc), but you don’t have to have a big air-spray setup and also don’t have to worry about the overspray, re-coat, and cleanup issues associated with an HVLP (high volume low pressure) air setup.
A little background info on my painting experience: my motorcycle painting is limited to my Honda NX650. That said, whether you’re shooting flat finish or a multi-layer colour change-scheme, there are some basic guidelines you can follow to make your life easier. Plan to spend about 70% of your involved time on prep, and about 30% on actually spraying. The spray period may actually take longer than the prep, but a large portion is waiting on paint to tack/dry/cure, so I don’t count that time.
Your engine can be a mess, but don't worry about that. Some simple Kitchen degreasers and some toothbrushes work great to remove the big chunks of oil and dirt. You could also go for the soda blaster approach, but make sure you mask off everything! (Take your for this)
Other nice tools to get the job done, are small steel and brass spiral tube brushes. The brass brushes are much softer and do not damage aluminium that soon/much. There are many (cheap) varieties here. Google it :)
This is by far the most important step in getting a paint job to look good. After removing the bits, parts and dirt, you’ll want to scuff the entire surface to be painted. Fresh paint doesn’t like to stick to a shiny finish, and scuffing also helps remove any surface unknowns like leftover wax or cleaner. I’ve found that 400-grit is the magic number, as any lower grit and you run the risk of ‘scratching’ instead of scuffing, and any higher is not going to help in removing anything like stubborn adhesive or the like.
Note: If you like to leave some parts polished (or want them to be), make sure you polish them now, while it is easier to mask them off than to polish them when the paint is already on!
With paint… comes masking tape. A lot of different widths, brands and stickiness. I disassemble the parts on the engine to make room and get a better result. Nobody wants unpainted areas when swapping for another set of pipes!
List of parts that were removed:
- Starter Engine
- Valve Covers
- Intake Manifold
I cleaned up the surfaces about 3 times and let it dry 48+ hours. Then, I blew it with high pres air to get all the remaining debris before painting.
This is the “fun” part about painting, because you can see the fruits of your hard prep work come to life. Spraying the paint is the most fun, but is also the most hazardous. Seriously. Want to kill some brain cells? Ignore the directions on the paint can that say to spray in a well-ventilated area. This is of course sarcasm, paint fumes are bad news. Make sure your area is a dry, warm and dust-free one as well.
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Also, make sure you use good quality paint and primer!
I used the VHT Flameproof Primer and Paint, which is used often by many bike builders I know.
For their instruction, click here.
Once you’ve got the primer shot, let it dry. If it’s the same type as your colour coat, you can start shooting colour after its kinda dry, within the recoat window. This means you either have to let it mostly dry and shoot it (usually in under an hour) or let it cure and then start the colour (1-2 days, depending). Primer doesn’t always have this long restriction on re-coat, which is a good thing, but make sure you read all the labels. Once you start shooting colour, however, you’re locked into the recoat windows laid out on your paint label, so make sure you’ve either got the time to finish, or the time to let it sit to finish later.
Note: Spray multiple thin layers. I can’t stress this point enough. Smoothing out 4 thin layers where each one almost completely covered the last is 1000 times easier than fixing the run you put in the paint because you just wanted to “colour that whole area on this pass”. Runs suck. Period. If they’re bad enough, you may have to let everything cure, sand that area down to the primer and re-spray. Save yourself this headache and just spray light layers. A good guide is that the surface looks like it’s about to be completely wet. Once it gets ‘completely wet’ any extra paint threatens to be too much for an area, and then the run happens. Believe me, that little speck you missed on the first coat after primer WILL get filled in a subsequent coat. Let it go. Better yet, find some scrap metal/plastic to practice spraying. If it’s your first attempt at painting, this will help a great deal.
So, to review:
1. Prep is 70% of the involved time and is by far the most important component to a good looking finish.
2. Polish before spraying
3. Pay attention to drying times for primers and paint in order to save time due to gouges/screwups.
4. Spray thin coats of colour to avoid runs.
5. Let it cure!
6. Smirk when someone asks who did your cool new paint job!
7. Use Loctite on all bolts that you reinstall.