Difficulty Repainting 1991 ST1100 Panniers

Hi,

My panniers had enough scuffs and scrapes, and the clear coat had worn away trying to remove the scuffs that I thought I would order some paint, primer, and rattle can it myself. I ordered the paint from automotivetouchup.com, using the paint code on the bike and prepped the pannier with sand paper and primed it according to directions on the can.After waiting the amount of time written, I lightly sanded with 600 grit sand paper, and shot it with color. The color looked a little off, but I decided go ahead and finish it. Anyway, after an hour, I noticed it spider cracking in places. It was a humid, overcast day, about 75-80 degrees.

After letting it sit overnight, I decided to look at the cracking, and underneath the base coat, it was gooey. I wound up using a putty knife to scrape the area and the black plastic was exposed in places.

What do I do now? Is the paint and primer wrong for this application?

Any thoughts would be appreciated.

drseth said:

What do I do now? Is the paint and primer wrong for this application?

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Could be or paint is "bad". If ya'll have humidity like we do, in the 90%+ range, that's not helping, and could be the reason.
Did the primer set up?
What type of paint was used?

EDIT: ST Owner article on pannier painting

Sounds like you did not let the paint dry enough before spraying the clear coat. You will need to remove the gooey mess re-sand and use less paint and make sure that the paint is dry before applying clear coat. Good luck.

Had the same issue on a total re-paint of all 17 pieces of tupperware. Since laquer and clear coated from factory, had to strip all pieces.
Laquer on top of enamel=okay........Enamel on top of laquer=not okay and WILL 'crackle,etc.'.

That's good to know. I took the panniers to a friend who owns a body shop. He is going to strip them, and repaint them for $125. Wish I had gone that route the first time.

Brant said:

Had the same issue on a total re-paint of all 17 pieces of tupperware. Since laquer and clear coated from factory, had to strip all pieces.
Laquer on top of enamel=okay........Enamel on top of laquer=not okay and WILL 'crackle,etc.'.

Click to expand...

There ya go! Lacquer is sprayed on in very thin coats, dries almost instantly and the solvent evaporates very quickly, leaving just the lacquer behind. Enamel dries much slower (it will "flow" for a while when applied) and it's solvent will attack lacquer (and sometimes other enamels) This is how lacquer can be used to "spot in" places on enamel paint jobs.

And some plastics are more sensitive to solvents than others, even on the same bike. When painting plastic parts, you may want to test paint the unseen side of a part to see if there is a reaction between primer/paint and plastic.

There are also specific primers for use on plastic parts, and you may even want to put a "flex agent" in the paint to make it less likely to crack when parts are removed and reinstalled for maintenance.

I like a polyurethane enamel for MC parts as it is a durable and flexible paint that will hold up well to weather.

That is good to know. I assumed that the paint I ordered would work for my application, but guess I was send the wrong paint.

You all have it backwards - generally lacquer over enamel IS NOT OK. Lacquer has much stronger solvents that will eat into the enamel and act like a paint stripper. That is probably why your 1st attempt failed using the automotive touchup paint . I'm guessing the automotive touchup paint was lacquer, they usually are because the lacquer is faster, and the factory paint is enamel, the lacquer will peel the base coat.
Enamel over lacquer is safe, we used to do that all the time repainting GM cars, back when Ford was using enamels and GM was using lacquers.
The easiest option today is a single stage urethane enamel, easy to apply and very durable once cured.
The best option if your guessing is to go with the body shop guys, they know what they are doing.

Highrider said:

The best option if your guessing is to go with the body shop guys, they know what they are doing.

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Having painted a couple bikes in the past I had pretty good luck with it, using quality automotive paint and an air sprayer. My weak link was my spraying technique, being that I was a novice. My experience with those jobs was the prep work took a good chunk of the time, the actual paint shooting was pretty quick.

So based on that I'm thinking you can probably do all the prep work on your bags yourself, then try to find a pro to shoot the paint for you, and it might cost less than you think. Not sure who would want to be bothered with such a small job though, so the price may get jacked up just because of the nuisance factor. Ask around, you might find someone to do the job on the side.

edit: sorry, missed post #5, apparently you've already done this.

Brant said:

Had the same issue on a total re-paint of all 17 pieces of tupperware. Since laquer and clear coated from factory, had to strip all pieces.
Laquer on top of enamel=okay........Enamel on top of laquer=not okay and WILL 'crackle,etc.'.

Click to expand...

I did have good results re-painting side covers on my 33yr.old Venturer. Local automotive paint supplier color match the original paint, and pre-mixed in a rattle can. Nozzle on can actually performed well. Paint was a single stage, which I did NOT clearcoat. Once hitting the surfaces, it layed smooth as glass, and is still that way today even thouht I did that 8yrs. ago. I initially though, wet sanded both pieces down to plastic, wiped with prep. solvent, shot a rattle can of high quality primer for plastic, then color. If it's just the sidecase lids your wanting to re-do, the same could be done initially by soda-blasting majority of paint off then wet sand.......JAT.

I just sprayed my left upper, lower and maint. panel with the Colorite paint. 4 steps: primer for raw plastic, silver undercoat, candy red and clearcoat. Excellent match to probably the toughest color to match: '93 Candy Red. Quite expensive though.
2 rattle cans of red $66. 1 base $33, 1 primer $12, 1 clear $12.
I'll post a pic to compare to my crashed bike once it's back on the road.
Aulia

I just bought the same kit from Colorite for 01 Wineberry. So I can't wait to see those pics.
Previous experience painting plastic in low humidity gave great results. But miserable results in moderate to high humidity.