How to Repair Fiberglass on Your Motorcycle

Teach yourself how to repair fiberglass for the next time your bike takes a tumble

Step 1Photography by Wes Allison

1. If you own a faired motorcycle, chances are you've had the near-heart attack experience of pricing replacement bodywork. Whether you've simply dropped Your Precious off its sidestand or performed a full-on face skid, the dollar signs can quickly soar into the quadruple digits. But don't fret; there's hope yet. Put away the JB Weld, duct tape and plastic repair kit-there's an easier and more sano way.

We had a partially damaged Body by Northstar tailsection that we put to the asphalt test at Daytona. The bodywork held up exceptionally well considering the severity of the crash, but still had a sizable hole and crack in the side. Note that this repair was done on a fiberglass section, but we have done the same procedure repeatedly with stock ABS fairings.

Step 2Photography by Wes Allison

2. Begin by cleaning up the damaged area. Wipe it down with contact cleaner or acetone, first making sure that it will not damage the bodywork. Next, use 280-grit sandpaper to completely roughen the surface around the damage, both on the interior and exterior. If you have a grinder-bit attachment for a drill, this works extremely well. Failure to create a scored surface will keep the fiberglass material from bonding correctly.

Step 2Photography by Wes Allison
Step 3Photography by Wes Allison

3. Next comes the messy part, which can be potentially brain-damaging and/or hallucinogenic if you're not wearing a respirator. First, clean the area again. Then, cut out pieces of fiberglass mat or cloth (mat is slightly stronger but cloth is easier to work with) in the shape desired. Then mix the fiberglass resin with the catalyst as per the instructions on the box. One or two ounces is all that is needed for most repairs. Fiberglass repair kits are available at most auto parts stores, and make sure you pick up some latex surgical gloves at the same time-this stuff is sticky.

Once the resin and catalyst have joined forces, you'll only have 20-25 minutes to work with the mixture before it begins to solidify. Use a paint brush and apply a thin layer of resin all around the interior damaged area.

Step 4Photography by Wes Allison

4. Now take the pieces of fiberglass cloth and carefully place them in the desired area. Situate the cloth so it best resembles the original shape of the fairing; the better it looks now, the easier it will be to complete the project later. Work the resin up through the cloth with the brush in order to keep the fiberglass in place. Continue to dab on resin until the region is completely wet-but not saturated-and there are no visible wrinkles or bubbles. Remember that it's crucial to fiberglass the outside of any cracks to ensure there's no breakage later.

Step 4Photography by Wes Allison
Step 4Photography by Wes Allison
Step 5Photography by Wes Allison

5. After the first layer has dried sufficiently, repeat the process, layering on more fiberglass while making sure not to exceed the original thickness of the fairing.

When the last application of cloth has dried entirely, use the grinder or 80-grit sandpaper to carefully knock down the excess fiberglass and resin-just make sure you don't grind all the way into the cloth, as that would weaken the structural integrity of the hardened fiberglass. Finally, scuff the entire area once again with 280-grit and clean it with acetone.

Step 6Photography by Wes Allison

6. The final step of the repair process involves making everything look right using polyester body filler (Bondo). Patience is the key when working with body filler. Do it right and nobody will know; do it wrong and your bike won't even pass the 50/50 beauty contest: 50 feet, 50 mph. If the area you're repairing is more than a few square inches, drill several very small holes in the fiberglass so the filler can squeeze through and secure itself to the fairing, similar to the function of finger holes in a bowling ball.

Step 7Photography by Wes Allison
Step 7Photography by Wes Allison

7. Mix the filler and hardener according to the instructions on the can. Using a thin, rubber-spreading card, begin applying thin "skim" coats over the fiberglass, making sure that some filler squeezes through the holes on the first coat. Feather the mixture onto the surrounding painted surface; the idea is to blend the filler onto the existing fairing without creating a rough edge, and to make the filler best resemble the origi-nal shape of the fairing. Oh, and by the way, you best hurry up-polyester filler is unspreadable after two minutes.

Step 8Photography by Wes Allison

8. Once the mixture has reached the consistency of your average block of Monterey Jack, start whittling it down with 80-grit sandpaper. Allow each application of filler to dry completely between coats, repeating the process until it is layered and sculpted to resemble the original fairing. For the final application, disperse a smooth layer of filler over the entire vicinity and let it dry. Sand it with 280-grit and then wet-sand it with 400-grit wet/dry sandpaper until you can no longer feel any scratches or imperfections in the plastic or filler.

Step 9Photography by Wes Allison

9. Just to demonstrate how good the final product looks, we shot on some white primer paint. When done properly, these methods are structurally sound and extremely effective. In fact, on the way home after our photo shoot, the tailsection fell out of the back of the SR Toyota T100 and landed right on the repaired area at 40 mph. There was no damage other than a few scratches.

So next time you find yourself staring at a cracked and splintered fairing, break out the fiberglass and body filler and give it a try. With a little patience, you'll have a good-looking fairing and a thicker wallet.

All finished!Photography by Wes Allison

How and why

Our partially destroyed guinea pig bodywork was volunteered by Body by Northstar (612/252-2924). All other supplies were acquired at a local auto parts store for the grand sum of $15. Not bad when compared with the cost of a new fairing. To prep your repair job for painting, see "Hands On," August '94. To complete a fairing rebuild, you will need the following supplies:

Be sure to have these supplies when repairing your bodywork.Photography by Wes Allison

    This article originally appeared in the October 1995 issue of Sport Rider.

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