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.
http://www.urethanesupply.com/PlastiFix/
I'm still not sure heat welding would not be more appropriate.





I'm sure someone here has tested this stuff and has the correct answer.

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

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...

Have a look at this and see what you think. I have heard good reports but have not used it myself.
http://www.plastex.net/index.php?pr=Home_Page

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...

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.

92kk

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.

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.

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?