BMW K bikes (Bricks)

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1Back to top Go down   Calling you Engineers Empty Calling you Engineers Sat Apr 20, 2013 11:18 pm


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1985 K100rs.
The "plastic" material that the side covers and the front radiator shell are made of is a somewhat soft almost "rubbery material that seems to be quite flexible. It is black or very dark grey, almost "soft" to the touch and roughs up easily with sandpaper.
I have had only limited success repairing this stuff. I have found 1 fact for sure: Fiberglass just doesn't stick to it at all.
I have had limited success in rebuilding 1 tab that was broken off a side cover. Tonight when preparing a used radiator shell for repaint a break was found in the thin area adjacent to the air intake grill. After severely roughing it up with 60 G sandpaper a fiberglass repair was affected. After the glass set, I found that the entire piece of fiberglass peeled off the base material cleanly. just doesn't stick.
The tab rebuild I did was done with plasti-fix and I'm reasonably happy with it.
I have just applied a "plasti-fix" repair to the broken radiator shell, reinforced with a piece of fiberglass tabe embedded in it.
Question: Can anyone tell me what exactly this rubbery black construction material is? Please don't answer unless you are SURE you know what the material is.
I have consulted several times with the plasti-fix manufacturer and they insist that it is not "Urethane" and that the powder/liquid plasti-fix kit is the proper item to fix this.
I'm still not sure heat welding would not be more appropriate.
Calling you Engineers Sam_3110
Calling you Engineers Sam_3111
Calling you Engineers Sam_3113
Calling you Engineers Sam_3114
Calling you Engineers Sam_3115
I'm sure someone here has tested this stuff and has the correct answer.


2Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sat Apr 20, 2013 11:50 pm


Not sure about the rubbery feel of your parts, but most of the 'plastics' are made of Fibron.

Stolen from another website. Think the explanation is pretty close to what I believe the stuff is.

"Fibron" was BMW's name for their proprietary Fiberglass, it is a very
high density sandwich of polyester resins, stranded fiberglass and
fillers(usually marble dust). These parts were molded in two piece
metal molds under heat and pressure, making a very strong composite.

Search repairs for that and you will find plenty. Most seem to use some sort of epoxy and not glass.

Good luck

1986 K100RT VIN 0093801K100RT with summer fairing for a northern visitor

Basic/2 6308802K100CJ  05/1988

K1100RS 0194321

3Back to top Go down   Calling you Engineers Empty I expect Sun Apr 21, 2013 12:14 am


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I expect that you are talking about the main fairing and the side lowers as well as the tail piece, etc. These are probably what you refer to as "Fibron" It is essentially shredded fiberglass & resins that is molded. That material takes fiberglass repair techniques very well as well as what is called "kitty hair".
Unfortunately, the side covers and radiator shell on the 1985 Krs are not made of Fibron.
They are more likely ABS or some kind of polypropylene mix.
Thanks for you speedy reply, but in this case it's not what I'm needing.
regards, ibj...


4Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sun Apr 21, 2013 3:59 am

RicK G

RicK G
Have a look at this and see what you think. I have heard good reports but have not used it myself.

"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama

Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki

5Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sun Apr 21, 2013 4:02 am

klompy the grey brick

klompy the grey brick
I have used poly tubing with a soldering iron with good results...indicating it is a plastic of some sort....araldite sticks to it ok as well....I imagine fibre glass resin would only peel off like its got release agent all over it.....
have fun now...

KKlompy Calling you Engineers 2854237993
"Grace" 1984 K100RS Silver VIN 0019026 Mitt eine Staintune Zorst.
"Olivia" 1997 K1100LT Dark Grey VIN WB1052600W0237453.

Chassis number0019026
Vehicle code0503
ModelK 100 RS 83 (0502 ( 0503 )
Body typeK 100 RS 83 (0502
Catalog modelECE
Production date1984 / 07

Calling you Engineers Au-log10


6Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sun Apr 21, 2013 4:30 am

92KK 84WW Olaf

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I have a broken tab on my right hand side cover. I also looked at this adhesion issue and no matter what it was it was difficult to find something that could be trusted to stay stuck. I actually came to the conclusion that it would be easier to make an L shaped aluminium tab and use a stud/screw through fixing from the outside face. It does leave a single flat round head/disc showing on the outside which can be painted or left in contrasting colour. The stud needs to have a decent diameter or large washer to spread the load and avoid pulling through.


1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500

7Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sun Apr 21, 2013 6:02 am

Hover K100

Hover K100
Silver member
Silver member
Polyester resin used in basic fiberglass kits is not a glue hence it peels off old fiberglass, try it with an epoxy resin after roughing up the surface for better adhesion. Epoxy will stick to polyester but not the other way round.

8Back to top Go down   Calling you Engineers Empty Re: Calling you Engineers Sun Apr 21, 2013 7:09 am


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I repaired the radiator cowling with a Portasol gas soldering iron and a strip of icecream container and a tiny black zippy tye both sweated down nicely to the cowling and mushed in as fill, with out letting go when cooled, all rubbed down and painted over now, so the plastic cant be too cranky a product. Mind you the soldering tip dont look to hot these days.

Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.

9Back to top Go down   Calling you Engineers Empty Thanks.....But Sun Apr 21, 2013 2:25 pm


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Thank You ALL for the multitude of nifty suggestions on various way to fix. As a matter of fact, both my side covers had some cobbled up L brackets to replace the lower tabs when I received them.
I will look further into the ideas suggesting Polyester resins, not sticking to fiberglass, that seems unrelated since we know the material is not fiberglass. I am curious as to what basic fiberglass repair kits describes.
I have a gallon of fiberglass resin from the local Napa body supply store along with the customary matt cloth. I didn't think to look at what it's actually made of, but I will. I can say it worked perfectly on the "Fibron" chopped fiberglass fairing parts.
I have also considered heat welding either with a hot air concentrator or a hot iron. I'm not sure which material "poly tubing" is or ice cream container?? I still wish to identify the actual material we are working with here........Can't be THAT difficult????
As to the link to Plastex....thank you, I have viewed it. It is essentially the same stuff that I have in the Plasti-fix product from urethane supply co.
So guys (engineers)......I still would like an answer to the base question. Not how you attempted to fix your parts, but "What is this material"? that the oem part is made of. I'm about to FedEx a complete side cover off to the urethane supply co people and ask them to identify it, but that seems extreme, given all the genuine EXPERTS we have here......LOL
What's it Made Of?


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