Toning down a Supertrapp on a K100RS

[Brickhead]

Hi All,

This has been in the back of my mind for a while - hoping one or more of the Brick-Wizards can weigh in on it:

Bought an '85 K100RS a couple of years ago, which had been fitted with a Supertrapp muffler by a previous owner. Bike runs like a top (of course), but the muffler is too loud, and it occaisionally backfires at low speed. When I went on Supertrapp's site to look into my options, there didn't seem to be any acknowledgement that a BMW K100 is a bike that would take a Supertrapp. Anyhoo, it seems that I can re-pack the muffler, or remove rings from inside of it to quiet the bike down (or both). Removing rings will apparently create a richer fuel mixture, though.

Anyone ever done this kind of thing on a K100RS? Is this a hard thing to accomplish? I want to avoid sacrificing horsees if possible, and I don't think I'll have the gumption to change anything if it means getting in over my head with adjustments to the overall tuning of the bike, since my wrenching skills are mediocre and it's not loud enough to get me arrested. And I can't afford to buy a new exhaust system.

I appreciate any feedback you all may have to offer, and if the guy who did this to my bike is still out there, I would be very grateful for a blow-by-blow of the procedure, including the specific model of muffler that has been used...

Thanks!
Brodie :)

[Bruce_C]

How many discs are in it now?
From my dirt bike days I found that you could drop down to 8-10 discs without hurting performance too much, if you can re-pack it that would be the way to go.
Be VERY CAREFUL removing the disc mounting screws. They are usually much longer than need be and are covered with carbon and such. When you get it apart replace the screws with #10-24 stainless steel Allen-head screws. The length of which should be 1/4-3/8" longer than the thickness of the disc pack. Coat the end of the threads with Led-plate or a hi-temp anti-seize compound.
What ever you do don't get strong with it and break or strip the disc screws or their welded thread bosses.
Bruce C

[Brickhead]

How many discs are in it now?
From my dirt bike days I found that you could drop down to 8-10 discs without hurting performance too much, if you can re-pack it that would be the way to go...


Hey Bruce,

thanks for the reply - not sure how many discs are currently installed, but there are only a few visible...could there be more inside the canister that are not visible without disassembly? I want to at least try re-packing it - the only thing that worries me, is that the how-to on Supertrapp's site isn't detailed enough for me - it assumes prior knowledge of things like re-installing a rivet and such...

[Bruce_C]

Brodie
Yes, you have to drill out the rivets around the rear of the can. Re-pack the tube and re-rivet the tube. If you are uncomfortable trying this, ask around a couple of dirt bike shops if they would do it for you.
That would cost a minimum of 1 hour labor. Probably as much as a used stock muffler on eBay or a junk yard.
Bruce C

[1990K1]

Check Summit Racing they have the "repacking kit" and Disc packs of various sizes. That's where I bought them from.

http://store.summitracing.com/default.asp?Ntt=supertrap&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp&x=16&y=9

http://store.summitracing.com/default.asp?Ntt=supertrap&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp&x=16&y=9

And if you have an "open" end cap you could tone it down with a "closed" one.

http://store.summitracing.com/default.asp?Ntt=supertrap&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp&x=16&y=9