Fixing Motorcycle Plastic Parts 101
Well... if you own a cruzer like a Yamaha Venture Royale, you will need to fix the plastic
sooner or later. I'm fixing one that had a sudden encounter with the freeway. I purchased
used replacement upper fairings from a seller and they were not in quite as good a condition as
advertised... but very repairable. Here's how you can do the repairs to yours.
Plastic or fiberglass?
Most bike body parts are made of injection molded ABS like plastic. So you need special/specific
glues. And they are great!!! and easy to get. The ABS plastic becomes brittle over the years of exposure
to engine heat, UV and temp. changes.
Basic Supplies...
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-Prep-All is the surface cleaner. Very aromatic so use out doors. -The epoxy is from Auto Zone, Checker or any large auto chain. It is specific to plastic. Regular epoxy will debond in a short time and fail. - 150 grit sandpaper for roughing the surface. - 3-6 oz. glass cloth used in fiberglass lay-up work. Lowes and Home Depot carry it and auto paint stores have it as well. People have used carbon fiber cloth or arimid/Kevlar cloth with great success. These are stronger, more expensive and a bit harder to deal with. - Latex gloves...however Prep-All eats through these so you might want to use Nitrol based gloves. |
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There are at least 2 manufacturers of epoxy that works on plastic. The auto paint supply stores have some newer formulations that are stronger... but it's tuff to buy them in small quantities.
This stuff really stinks !!! Be warned. It sets firm in about 10 min. and is flexible but cured overnight.
DO NOT use standard epoxy. It will delaminate and fail. |
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This thin glue is amazing. With an needle tipped applicator you can wick it into the smallest cracks. It melts the plastic and re-fuse's it back together. It takes about 10 min. to blow off and it cures in about an hour.
I found it at a store that supplies plastics. |
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If there is one trick that will make you life easier, it's this rotary fabric cutter. This is THE secret trick to cutting the fiberglass cloth without saying bad words. Just about anywhere that sells fabric has these. |
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Hairline cracks are fixed with the thin glue. I wick this in prior to any fix for extra strength. |
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Open the crack slightly and the drop of glue will wick down the crack. Let it set for an hour prior to reinstalling. |
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You're going to do the repair in the inside of the plastic part. Wipe the area down with the Prep-All and a clean rag. Sand the entire area with the 150 grit sandpaper. Then, wipe it down again with Prep-All.
Now, wick some of the thin glue into the crack and let it set for 30 min. If the crack or broken area was a stress related fracture, use masking tape to hold the part together while the thin glue cures. |
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Lay out the fabric, mark a piece that will be 1/2" or more larger all the way around the crack to be repaired. Use the roller cutter to cut it out. It's better and stronger to cut the fabric so the weave runs at 45 degrees to the crack. |
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Squeeze equal parts of the epoxy onto a piece of cardboard. |
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Mix the epoxy for at lease 1 min. NO LESS!!! If it's not well mixed , it will not cure as strong. Now is when it starts to stink. This stuff will clear a room. |
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Wet the plastic surface with the epoxy. |
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Push the fabric into the wet epoxy and use a gloved finger to smush it around. When the fabric is wetted properly, the fabric will appear to be transparent. If it's white, like you see around the edges here, it is not properly wetted. Use the mixing stick to spread more epoxy over the fabric.
Working time is about 5 min. until it starts to flash which is plenty.
A razor blade is perfect for trimming off the excess. |
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If the area is already structurally thin like the area around the cowl intakes, multiple layers will be needed. You can lay these up even if the first layer is starting to cure. Make sure each layer has the weave running 45 degrees offset from the other. |
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This lower fairing tab was completely missing. Just cut and file the fairing side square. The tab was cut from the fairing that were blown up in the crash, using a Dremel. File the butting edges so they match as tightly as possible.. |
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The backside of the tab fix is three layers of cloth, each somewhat smaller than the one under it. You will be surprised at how strong this becomes when cured. Let this set overnight for a full cure. Then spray the area with semi gloss or flat black paint to hide the light colored fabric. |
It's all to simple to do. I've had great success with this method and rarely has a fixed part failed
at the repair.
