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Thread: tuning for a new exhaust

  1. #1

    tuning for a new exhaust

    I just found a set of new Mac two into one headers for my 82 R 100. Sure doesn't sound like my father's Beemer! Do I need to do anything with my carb settings? The bike seems to be running fine with decent power throughout the RPM range. geoff

  2. #2
    Registered User TRJeff's Avatar
    Join Date
    Mar 2003
    Two Rivers Wi.

    Thumbs up tuning

    I have the same exhaust on a 1983, All I did was raise the needles one notch and opened the idle mixture 1/4 turn to get ride of the decell popping. Engine timing stayed stock. Runs great nice snarl and fuel milage is fine.

  3. #3
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    Since your and all '81-on Airheads have two exhaust crossovers, you can assume the entire system aft of the first crossover, including the second crossover, is available to each cylinder.

    With a 2->1 exhaust system, you have effectively reduced the size of the exhaust system.

    You may find the following interesting:
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  4. #4
    Well actually, I think that I increased the size of my exhaust system. Seems as half the stock system fell off the bike five miles south of Marble Falls, TX!!!! And of course it's got gobs more power! You can hear it!!!! Beside all of those great improvements, I get to motor back and forth, back and forth, back and forth early Sunday morning in front of my neighbor's house, the big Harley guy!!

  5. #5
    Howdy All !!!! my first time in here but I didn't want to start a new thread just to say hello.

    Got to have more power 'cuz you can hear it?? I don't mean to rain on anyone's parade but I don't think that is necessarily a true statement. More will make more noise...but more noise doesn't always make more power.

    Either way, if you love the pipes, ride 'em. But if the noise level is up, then the back pressure is probably then the carbs need to flow more fuel to keep up with the increased air flow. Just change the jets up one size at a time until it runs worse, then go back to where it ran great. If the first change up makes it worse, you may have just been too rich before...

  6. #6
    Tongue was firmly in cheek on that one! I am still trying to decide if I should mess with the jets. The only problem is that I am a big believer in the don't fix it if it ain't broke school of thought. Bike seemed to run well during a test run. First priority is to get the back wheel back on! I finally got around to changing the rear tire last Sunday only to find that my new tube had a pinhole leak. Picked up a tube but I haven't had time to put the mess back together yet. Oh well!

  7. #7
    Join Date
    May 2003
    Manitowoc, Wisconsin
    Well, in days gone by, one would change the jets, install new plugs, go for a ride(ensuring you get up on the main jets), then read the plugs. Adjust accordingly. Cost was in jets and new plugs. Now if you have access to an exhaust gas analyzer(doesn't everybody?) or a dyno, the process is simpler. Not trying to be facetious, but that's how we USED to do it. Look for the nice light-tan color on the insulator.
    F.O.G.Rider, Rounder #6,
    BMWRA Wisconsin Region Rep
    MOA Biergarten co-chair

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