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Thread: Repair of fiberglass fairing parts

  1. #1
    Seattle-area Rounder OfficerImpersonator's Avatar
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    Repair of fiberglass fairing parts

    I did a search of all threads and didn't find an answer to my question.

    Does anyone have any experience repairing fiberglass fairing parts? The previous owner of my K75S had a very low speed low-side that put a bit of rash on the right upper fairing and a couple of cracks that go all the way through the side of the belly pan.

    I spoke with a friend who owns an autobody shop and he described a laborious and messy process of cutting out the bad parts and filling in the voids with many many alternating layers of glass and epoxy. He said I'd be itching for days if I attempted a home repair of fiberglass.

    Has anyone discovered or invented a shortcut? I would think that it would be easier to put some sort of patch on the back to hold the severed pieces together, and then use some sort of filler to fill in and conceal the cracks.

    I'll take some photos of the damage I'm trying to repair and upload them a bit later, as I'm sure that would further clarify the scope of my project.
    Seattle, WA
    2012 R1200GSA
    2002 R1150RT-P
    1992 K75S sold

  2. #2
    BUDDINGGEEZER
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    Fairing repair

    I just recently repaired a 1987 K100lt that had been down on the left side. It is not very hard to get a good repair. I too had several cracks in upper, lower and rash on mirror. I took a dremmel tool with the little round sanding wheel and groung the back side of the crack. I went half way through. this makes a U shape furrow. I used an Epoxy putty. JB weld would do , but Bondo makes an Epoxy putty ( not Bondo body filler). After curing I ground the finish side the same way leaving a thin line of the epoxy on the back side. Fill with Epoxy. This will make a repair stronger than the original. Then lightly grind that in order to fill with Bondo body putty. sand 325 grit, primer, sand 600 grit, paint with color coat, do not sand, paint with clear coat, sand 2000 grit and buff. I had not painted in 30 years and my bike came out great. I used a PPG brand paint in Toyota dark grey mica.

    I believe the picture is #311 on page 21 of K bike pictures.

    Be sue to use Epoxy. Polyester is not strong enough. All frayed edges need to be ground or cut smooth if a hole is in the fairing. One pint of paint should give 2 coats of color, and then 2 coats of clear.

    You can look me up ans send me a message with your phone number and I'll call and answer ???????????

  3. #3
    3 Red Bricks
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    You might want to read this:http://www.largiader.com/k75/repair.html.

    I have had no experience using these methods, but it's the only article I have found.

    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  4. #4
    Curmudgeon nrpetersen's Avatar
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    Budding Geezer is right. You have to grind out and feather most of the the crack from the back side & then back fill it with layers of glass cloth and epoxy.

  5. #5
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    repair

    I have done extensive work with fiberglass, polyester and epoxy resins. It is incredible stuff but good prep work is essential. Roughing up, feathering out and using reinforcement over fillers is important to get a good bond. I've used several epoxies and prefer WEST becuz of its availability. its product line of fillers and technical information on usage. But it is expensive unless compared to the complete job at a body shop. The idea that paint doesn't hide anything is so true and working with basecoat/clearcoat is easy to use once you understand some things and follow the directions. I've recently rebuilt the "plastic" on a K1100LT and few will be able to tell what went on behind the scenes. Good lick and let us know how it goes1

  6. #6
    Seattle-area Rounder OfficerImpersonator's Avatar
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    This is all great information, and reassuring as well. Thanks to your advice, I think I'm going to give the repair job a try.

    Let's see what the wife says when I tell her I need to buy a Dremel Moto-Tool! Any excuse to buy a new tool...
    Seattle, WA
    2012 R1200GSA
    2002 R1150RT-P
    1992 K75S sold

  7. #7
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    You certain its fiberglass? I work at a autobody shop and have fixed allot of bikes too and I've yet to find one made of fiberglass, most are made of ABS, polypropylene or similar plastic. I haven't looked close at a k75 fairing to see so it might be. You need to find out because it makes a huge difference how you repair it.
    If its another plastic airless welders work well for repairs but if its fiberglass you really need to do the time consuming repair if you want it to stand up and look good. There will be people that tell you all you need is some JB weld and some popsicle sticks but if it was my bike I'd want to fix it right the first time.

  8. #8
    looking for a coal mine knary's Avatar
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    It's fiberglass. I repaired various fairing pieces on my old K75s after an unpleasant encounter with Monitor pass. It's tedious, but very doable. Wear some protective gear to keep the fiberglass off of you. The fiberglass is structural, but doesn't and can't cleanly fill every bit of damage. Once the piece is strong again, use the filler to make it clean and nice.

    The short version:

    1. Grind out the broken area, removing fragile shards and making room for the fiberglass.
    2. Clean it thoroughly.
    3. Apply fiberglass and epoxy. Where possible, apply fiberglass to both the front and back of the damaged area.
    4. Scuff, clean, and fill with a body filler intended for flexible parts. You might get away with regular old bondo (I did), but it may crack in a high flex area.
    5. Sand it all down.
    6. Paint.
    7. Look back and wonder if it was worth the effort.

    The repairs I made look like they're holding up just fine (I sometimes see my old bike, four years after the sale and eight years after the repair).

  9. #9
    kayseventyfive
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    Quote Originally Posted by knary View Post
    You might get away with regular old bondo (I did), but it may crack in a high flex area.

    Using Bondo is taking a chance on anything that vibrates or flexes. Use epoxy putty.

  10. #10
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    Ok like others said wear some latex gloves to keep the glass and resin off you and try to keep clean.

    You'll need to grind out the crack in the shape of a "V" so its deepest in the middle and gradually gets shallower away from the crack(you'll do this to both sides for the strongest bond)
    You'll cut fiberglass cloth in a thin strip to lay in the crack then wet with resin(too much resin and it will be heavy and won't be strong, too little and it will be weak too) Then cut another strip wider then the first and lay it over the first one and wipe with resin. Keep doing this till its almost even with the surface and comes out to the edge of your "V"
    After that you'll need a flexable body filler to apply and sand down to make it smooth and even.
    Paint won't hide any blemishes infact it magnifies it so 90% of a good paint job is the prep work, painting is the easy part.

    Repairing fiberglass isn't hard but it is messy and time consuming.

  11. #11
    From MARS
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    Repairing of fiberglass fairing parts

    If you are going to be grinding/sanding fiberglass, make damn sure you wear a good respirator. A dust mask is not adequate. Fiberglass particles will stick into the lining of the lungs, if breathed in, and NEVER go away. When I worked on yachts, I had a doctor tell me that if a person worked with fiberglass and smoked anything, they needn't bother saving for retirement 'cause they wouldn't make it.

  12. #12
    BMW uber alles! Zagando's Avatar
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    Bump for a great thread on fiberglass repair...

    Just ran across this old fiberglass thread while searching "K75 fiberglass" to ascertain or make certain that my "plastic" body parts are actually fiberglass---before I begin my painting preparation.

    I also have some cracked/chipped fairing and belly pan pieces that need some looking after, too. The chips are small, 1/4" or so and I'm hoping to get by well enough by cleaning and filling them with epoxy putty and sanding them before the primer and base coats go on.

    The belly pan has an area of slight cracking about 3" around so there again I may try the putty on the back as well as the front sides and then sand smooth. Doesn't seem bad enough that it would require cloth and resin and then putty---I hope these assumptions are correct.

    If anyone experience begs to differ, I'm all ears, but I think the damage I speak of is very minor and doesn't need the full monty, sotospeak. I do like Budding Geezer's approach and suspect that's the ticket in my particular case.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  13. #13
    Dale Rudolph
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    Have you tried a place like Beemerboneyard to see if they might have replacement
    pieces? They may be able to steer you to someone who has them. Seems like that
    would be the easiest way.

  14. #14
    BMW uber alles! Zagando's Avatar
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    I'm not after replacement pieces---I'm restoring/refinishing what I already have, thank you.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  15. #15
    BUDDINGGEEZER
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    The fairing pieces are a fiberglass filled plastic. Epoxy putty works well. Here is a finished example.

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    Ralph Sims
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