Who makes Yamaha RD400 expansion chambers

Discussion in 'Motorbike Technical Discussion' started by glenb900, Feb 1, 2006.

  1. glenb900

    glenb900 Guest

    Who Still makes Yamaha RD400 expansion chambers? Is DG still around?
    What would be the best expansion chambers to replace stock pipes with
    no mods to the motor, carbs, airbox? The original pipes are damaged and
    would like to replace with expansion chambers and hopefully not have to
    re-jet or add K&N air filters. Any shops or website stores that
    specialize in Yamaha RD400 parts and exhausts? If I had to re-jet with
    K&N filters what size would you recommend with suggest pipe? Right now
    motor is completely stock. I'm not looking for used original pipes,
    just want to replace with something that looks sporty. This is just for
    the street, not racing.
    glenb900, Feb 1, 2006
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  2. glenb900

    Alfred J. Guest

    The last time I checked, Specialists II in Burbank, CA was still making
    expansion chambers. DG was in the latest www.denniskirk.com catalog.
    That's silly. What do you think an expansion chamber is for, just
    looks? An expansion chamber acoustically supercharges a 2-stroke engine
    at a certain RPM with a plus/minus 6 or 7 psi. How is the engine
    supposed to get enough fuel to cope with all that extra air if you
    don't rejet? How's the engine supposed to breathe with the stock
    See above.
    See above Specialists II.
    It depends on the track you are actually racing on or if you're posing
    by the bike at some burger stand. I told some guys they needed 150 main
    jets in their machine and they put 115 main jets in and they burned a
    hole in a piston and blew up their motor.

    By the way, you probably don't know enough about carburetors to be
    asking internet strangers for jet numbers. You'd run out and buy the
    wrong kind because you don't know the difference between hex jets and
    round jets.

    Gary Schumake of Spec II would know. But if you're clueless, he will
    sell you anything he's got to put your money in his cash register.
    Don't ask how I know that. Or look up a tuner named Steve Bigansky who
    did a lot of tuning for Del Amo Yamaha and Nick Ienatsch and Kent
    There's no point in buying expansion chambers if you're not going to
    increase the compression ratio, tweak the carbs and port the cylinder
    for more power at higher RPM.
    So look for a used 600cc 4-stroke like a CBR-600. Two-stroke motorcycle
    tuning is for the dedicated 2-stroke nut, it's not for you. You're
    probably just a poser, wasting our time with silly questions about
    Alfred J., Feb 1, 2006
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  3. glenb900

    Leon Guest

    When I fitted expansion chambers to my RD350, many years ago, I had to
    use *much* larger main jets in the carbs. That was all I did, IIRC.
    Performance was much better but the fuel consumption was very poor. I
    had to set the ignition timing every couple of weeks, it was very

    Leon, Feb 1, 2006
  4. glenb900

    Bill Smith Guest

    Expansion chambers require a complete re-think top to bottom in the
    carbs to get the most out of them, and if you aren't willing to do the
    porting and head mods to go with the pipes it's going to be peaky and
    unpleasant to ride, along with being unreliable.

    An RD can be made to perform very well if you are willing to do the
    work, and learn what you need to. If you aren't, find some stock
    pipes, no matter what they cost, it will definitely be cheaper.

    Bill Smith
    Bill Smith, Feb 5, 2006
  5. glenb900

    Tod Guest

    Check out the USA2strokers forum at http://usa2stroker.com/forum/. You can
    find lots of info
    and recommendations there.
    Tod, Feb 11, 2006
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