Paint question

I’m trying to paint a replacement side cover. When I got the side cover is had been repainted with a blobby satin black finish. I sanded it down to what I assume was the original paint which was black with gold metal flake (were the 550 Seca colors 81-white, 82-red, 83-black?). This actually looked quite nice but of course doesn’t go with my red bike.

Some of you might cringe now but I used spray enamel. (If I had the $ for a compressor and sprayer and specialty paint would I be riding a 27 year old bike I bought for $350?) Two coats went fine until I went to do some fine wet sanding for the final coat. It started cracking up. I don’t know what this is called but it looks like the two coats I put on were stretched over the cover and started tearing. It wasn’t peeling off, just cracks in the finish. Does this mean the original paint is a lacquer? Do I need to use lacquer or sand down to plastic to get a good result?

 

Sounds like lacquer check or lacquer crack. It's definitely a chemical reaction to something already on the bike. I'd sand deeper and prime heavier, then resand.

I've painted several with spray bombs over the years and while they can be made to look good, there's NO hardener in it so it takes forever to cure (dry completely through). It'll scratch easily and gas spillage will go right through it.

 

Could also be lack of humidity control or leaving too much time, or too little time between coats.

 

Can't put anything over lacquer except:

- more lacquer
- epoxy

Solutions:

- sand everything off down to bare plastic, start over
- sand back down to smooth, use EPOXY primer-sealer (we carry this that includes a hardener)
- primer over the epoxy sealer with a urethane primer
- now paint with any type of paint you wish!

 

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(Can't put anything over lacquer except:

- more lacquer
- epoxy )


Not true. Most primers are lacquer based. If you use and enamel with no catalyst it will stay soft for a very long time and shouldn't be color sanded. Cracking can also be caused by the solvent in the bottom coat still being wet. That's why you have flash time between coats. If your can is lacquer based and you shoot over enamel it will lift. The solvents attack the enamel. In reverse this is not the case. I have used lacquer for stripes many times and then come back with a hardened enamel over it.
One thing is for sure. If you strip it and allow flash time, you should come up with a presentable finish---all other things being accounted for.

 

You mean the plastic side cover pieces? If so, I'd use a chemical stripper, then sand, to get to whatever the bare material is. I'd go through the old paint, or it will likely not stick for long.

In either case, the primer is going to be the key. I like two coats of primer, let cure, wet sand with 1200 or finer (to get the surface REALLY smooth), then one final coat of primer. Then, when you paint on the spraypaint, do one coat so that it doesn't entirely cover the primer. Let dry. Do second coat so that it covers, but still looks kind of flatish (not glossy). Let dry. Then, with the third coat, spray until it looks wet. Don't over spray, or you will get sags and runs.

When you paint, make sure to have LOTS of light from at least two directions. Makes a huge difference. HTH.

BTW, if you can find an auto paint store, you can get better solvent-based paint that will flash (solvent will evaporate out) quicker. You can also excellerate the flash time by using a hair dryer or heat gun. The paint might be a bit more expensive than Krylon, but it will work better.

 

I personally wouldn't use chemical stripper on the plastic. If it doesn't outright melt it, it will most likely soften it.