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Thread: 1985 K100RS aftermarket exhaust.

  1. #1
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    1985 K100RS aftermarket exhaust.

    I'm thinking about replacing the stock, bulky exhaust with something aftermarket. There are a few options out there but not many. My question is with respect to reduction of back pressure and mixture. How does the fuel injection compensate for this, or does it? I've re-jetted carbureted bikes but fuel injection.........

  2. #2
    The original Luft Injection system compensates because it is constantly measuring the amount of air entering the engine. That is why it is important to not have any air leaks in the intake side or the engine breather side. I installed a Remus system on mine several years ago since it was about the only one available new. It's louder than I would prefer but not obnoxious.

    Frank
    '17 R1200RS, '03 R1100S BCR#6/200, '85 K100/1100RS, '16 R1200RS (gone) '11 R1200RT (gone) '05 R1200ST (gone) '99 R1100S (gone) '96 Ducati 900SS/SP (gone) '92 K100RS (gone) 500,000+ BMW miles

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    The FIE will compensate, as it measures the airflow and injects accordingly.
    While you may lose some weight, and that ugly boxy look, but don't expect any power increase. I've done dyno pulls on an 85 K100RS with stock and Luftmeister exhausts. No difference in power output.

  4. #4
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by JeffDiCarlo View Post
    The FIE will compensate, as it measures the airflow and injects accordingly.
    While you may lose some weight, and that ugly boxy look, but don't expect any power increase. I've done dyno pulls on an 85 K100RS with stock and Luftmeister exhausts. No difference in power output.
    True. A number of years ago several of the K-bike guru members of the Internet BMW Rides club did dyno runs between the stock exhaust and a Staintune. The data said that there was only a very, very small increase in horsepower and then only at two or three new peaks in the hp curve, and these were offset by a couple of drops in hp at other parts of the curve. Overall they concluded that the hp and torque curves were smoother (i.e. better) with the stock exhaust. You can change the stock K-bike exhaust but unfortunately all you will get is a different sound and a lighter wallet.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

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    MontanaMark kmellzey's Avatar
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    I have a Staintune exhaust on my 92 K75S. While I doubt it does anything for the horsepower, I surely do love the sound it makes. I'm not sure you can out-engineer the BMW folks.

    Cheers,
    Mark

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    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by kmellzey View Post
    I have a Staintune exhaust on my 92 K75S. While I doubt it does anything for the horsepower, I surely do love the sound it makes. I'm not sure you can out-engineer the BMW folks.

    Cheers,
    Mark
    I agree, at least with exhaust systems designed prior to environmental regulations. Replacing the stock exhaust (with cat) on my 2003 K1200RS with a Remus exhaust saved about 15lbs and added 12+ rear wheel horsepower. This is from dyno runs at my local dealer. Oh, and the Remus added another 2 to 3 mpg.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

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    Registered User Rinty's Avatar
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    Quote Originally Posted by GREGFEELER View Post
    Replacing the stock exhaust (with cat) on my 2003 K1200RS with a Remus exhaust saved about 15lbs and added 12+ rear wheel horsepower...
    Wow.

    My indie had also told me you'd get more power out of a boxer with the Remus.

    I've always liked them for their excellent quality and lighter weight.

    If you go to their website, they have a picture of their impressive R & D facility.
    Rinty

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    Thanks for all your input, guys. I'm not interested in more power. Currently looking into BSK SpeedWorks. I have been in contact with them and they have exhaust components that will fit and allow me to keep all stock components.

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    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by Rinty View Post
    Wow.

    My indie had also told me you'd get more power out of a boxer with the Remus.

    I've always liked them for their excellent quality and lighter weight.

    If you go to their website, they have a picture of their impressive R & D facility.
    On my K12RS the Remus made a noticeable increase in power.
    Greg Feeler
    Ambassador & amateur K-Bike collector, it seems
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

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    Quote Originally Posted by GREGFEELER View Post
    On my K12RS the Remus made a noticeable increase in power.
    I'm shopping a K12RS with a Remus exhaust. When the owner had it installed, the shop put it on a dyno for him: 108 HP peak.

    BMW rates the stock bike at 130 HP, probably at the crank. If you figure a 15% loss to the wheel you end up with 110 HP. Without a back-to-back, it's all speculation, but 108 with the Remus doesn't sound like a big boost to me.

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    Is the Remus even available anymore for the early K-bikes?

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    Registered User barryg's Avatar
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    SuperTrapp Exhaust System Loud

    The fuel injection system on a K bike can handle a aftermarket exhaust. Back over 20 years ago I took the stock exhaust off my K100RT and installed a complete SuperTrapp system. Really cool at first. Didnít take long for me to tire of it. At idle it was relatively quiet, but at speed 60-80 mph it was loud even with ear plugs. Not only was it loud, but it had an abusive sound. I found myself trying to outrun the sound. Sad. Removed that system and put the stock system back in. Saved the SuperTrapp, may find a Ď85 K100 and build a hot rod.

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    Well, FWIW I got my hands on a Remus and it was delivered yesterday. Unfortunately no more riding this year in the Great White North. It will be spring before I get to ride with the new pipe and the RaceTech emulators. Fun projects ahead this winter.

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    Quote Originally Posted by mcmlcccvrs View Post
    Is the Remus even available anymore for the early K-bikes?
    I've been told it is not.
    I sold off the one I just obtained (bought the whole bike) to a guy who had been looking and found nothing new, and very few used available.

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    [QUOTE=JeffDiCarlo;1224608]I've been told it is not.
    I sold off the one I just obtained (bought the whole bike) to a guy who had been looking and found nothing new, and very few used available.[/QUOTE at


    I can certainly understand coming to that conclusion, but that simply isn't the case. Remus is ending production of their K100 systems this year. This is from an email exchange I had with Uwe Grasser, Head of Sales at Remus in Barnbach, Austria. I contacted them about something else and a brief exchange of emails ensued. He said they are being offered to the US market. No demand here? I can only speculate. If you want one you can get them.

    Once I made the decision that Remus is what I wanted I found them in 5 minutes. Remus-Canada.com didn't even list the K100's in their available selection of BMW motorcycles.

    I purchased mine from Germany, but it is what it is.
    Last edited by mcmlcccvrs; 10-23-2020 at 02:20 PM.

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