Suzuki 2 Strokes

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Gordon, fiberglass paints just about like metal, you just have to be sure there are no hairline cracks or they will come right back through the paint once it is cured. I would use a sealer type primer.
Ogri is probably the expert here.

Wayne

I've painted fiberglass which was embedded in plastic bodywork. I used the same paint and methods as on metal. No problems.



Lane

Are you sure you want to get my take on this? You know my response will be long drawn out and read like a reference manual since paint is the only thing I know with any amount of certainty.....

Preparation of the fiberglass is where most have issues. The surface of fiberglass is very porous so adhesion should never be an issue if the part is prepared properly.

To ensure good adhesion the surface must be clean of mold release, road grime or any other contaminate. To remove this and any other contaminates, mix isopropal(SP?) alcohol and water 1:1. NEVER use a solvent based cleaner on plastic or fiberglass. The solvent will be absorbed in the pores of the fiberglass and can cause adhesion issues down the road. Using clean rags (paper towels would work well here), saturate your towel with your alcohol and water mix and wipe down a small area at a time, take another towel and dry the area you just wiped. Make sure the alcohol and water does not dry on the surface before being wiped off. The mix will float any contaminates to the surface and you wipe them off before the mix dries dropping the contaminates back on the surface. Do this step prior to sanding as well as prior to tacking and painting.

The caveat to fiberglass is that it may have pinholes that are difficult to see until the part is painted. Sometimes these can be sanded out in the gelcoat, but I would not depend on it. Usually, the more you sand the more pinholes are exposed.
The way to find these pinholes is to wipe a liberal amount of alcohol across the part and watch it evaporate. The alcohol in the pinholes will take a moment longer to evaporate than that on the surface.
The best process I have found for filling pinholes is to use a good two part polyester glazing putty, and use a razor blade for your applicator. This allows you to press the putty into the pinhole without leaving an excessive amount around it to sand off.

Other than these issues, painting fiberglass is no different than metal. No adhesion promotors or special primers should be needed. The same primer you use on metal will work on the fiberglass if fill is needed.

Wayne makes a good point about cracks in the surface.
Use a die grinder to remove the crack. This will leave a deep gouge in the surface but will remove the crack and provide more surface area for your filler. Grind the area around the crack you just removed so that it is a few mils lower than the surface, then apply your filler. This will make your repair as strong or stronger than the remainder of the part.
Prime with a good two part urethane to ensure flexibility as well as long term fill with less shrinkage.

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This evening, part of a bottle of Scotch will be ceremoniously sacrificed in your names.

Way to go, Gordon....making the big sacrifice by taking one for the team....
right ??!!??

Use "High Fill" or "High Build" primer on it and you'll see if there any pin holes. You can keep sanding and building with the primerand that will take care of the small holes/imperfections. Glazing puddy for the larger ones.

Other than that no difference.

I've got a set of ancient saddle bags that I'll be doing the same thing with.