Hello,
I need suggestions on the materials and methods used to rebuild the interior portions of the baffle on my 1985 K100RS.
Thanks,
Jim

I assume you are talking about your exhaust system. If that is the case, I would just go to eBay and get a used muffler that looks to be in good condition. They are out there for reasonable money since so many bricks are being hacked into cafe or scrambler customs these days.

After searching the internet, I realized I may not have been asking the question correctly.  I found stainless muffler rebuild material that I will use to rebuild the baffle sound absorption material.  International Steel Wool sells what they refer to as "Muff Pack Muffler Repacking Kit".  Purchased from Amazon.
Thanks,
Jim

Please post a thread on what you do with lots of photos. I have never heard of repacking a stock exhaust, but the information may come in handy some day.

The stock exhaust is not an absorption system. The muffler has chambers, with tubes allowing the gas fow to pass to the exit.
Your steel wool will be useless.
If you have an aftermarket exhaust, some use the absorption system.
Steel wool is not a very sustainable material, it is thin, rusts and burns easily.
Glass wool is more resistant.
A good tip is to use different densities of wool to absorb different frequencies. Do not press wool inside the muffler, it has to be loosen to be efficient.

jbt wrote:The stock exhaust is not an absorption system. The muffler has chambers, with tubes allowing the gas fow to pass to the exit.

Here's a partial look. Packing it with anything—if it were possible—would restrict flow and affect performance. Go with finding a used one. Is the exhaust is popping during deceleration? 

Thank you so much for your replies.  I appreciate everyone's patience with my ignorance!!
It is a stock exhaust as far as I can tell. 
Photos show the metallic material full of carbon deposits I am talking about replacing.  Perhaps I should just leave it out and just re-assemble with no material.

Thanks,
Jim

Looks like an aftermarket exhaust. Maybe somebody can chime in with who made it. Stock systems are baffled with controlled gas expansion chambers, etc. and don't use packing.

As far as packing what you have, if I couldn't find what the manufacturer recommends, I would probably go with a fairly coarse stainless steel wool. Less risk of corrosion from acids in the exhaust gases, and a higher melting point than regular steel wool. I'd avoid fiberglass as it breaks down and get blown out. And I don't think you want to breathe the microscopic bits that would be floating around when you run the engine in the garage.

Possibly a Mac exhaust.
Regards Martin.

Maybe even a Kenworth K100 cabover exhaust, looks better.

The black coating (and the fact that there still be a black coating!) let me think this is a Luftmeister exhaust.
The shape of the rear cylinder tube is typical.

Find a good s/h standard exhaust. It might not be a pretty as a round exhaust system but tests waybackwhen showed that BMW had got it completely right and none of the aftermarket manufacturers were able to extract any more power out of the engine. It also has the advantage of being stainless steel, which means they're relatively cheap because they don't fall to pieces easily.

Excellent comments.  I searched on Luftmeister exhaust and found what looks exactly like it. 

There are other comments such as the following that lead me to believe I am headed in the right direction with the stainless steel wool.  Worst case I can remove again and just try without.

"Luftys sound great if you can keep the can packed, I never could and got to like it with no packing"

and

"Google muffler packing.  Amazon, most bike shops sell it.  Usually fiberglass but I've seen stainless steel wool that may last longer."

Does anyone have suggestions on surface repairs on the header tubes, and paint or jet-hot once repaired?

The hipsters who build cafe bikes use muffler wrap. I think it's supposed to make more power or something. While an acquired taste, it really doesn't look too bad when done neatly.

Downside as I see it is that your pipes do not appear to be stainless and wrap would probably accelerate the corrosion.

Try using heatproof ceramic spray paint or get it professionally done.
Regards Martin.

Point-Seven-five wrote:The hipsters who build cafe bikes use muffler wrap.  I think it's supposed to make more power or something. 

It's bullshit.
It used to be necessary on lateral old car engines, where some issues appeared due to the poor compression ratio and the unadapted shape of the combustion chamber and exhaust. Packing the exhaust helped to reduce the condensation phenomenon when the gas meet a low pressure envidonment outside the engine.
Then, with engine more performant, it was useful under closed bonnets on hot rods, the exhaust was prone to create heat managment problems with the fuel.
Today, apart on very hi performance engines (drag racing), and particularly on motorcycles with open air engines, it's useless and may even be counter productive.
It's a pure fashion victim gimmick.