RD400 Project

Discussion in '2 smokers' started by Mike Butt, Aug 6, 2010.

  1. Mike Butt

    Mike Butt Agent Provocateur

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    So I bought an RD400, 1977, off of Road Rash.

    Promptly I did the equivalent of this to it:

    [​IMG]

    So we threw a party to fix it:

    [​IMG]

    Everyone gathered around (particularly Dagwood who seemed to know what he was doing):

    [​IMG]

    Dagwood calling me an idiot:

    [​IMG]

    And me making idiot moves:

    [​IMG]

    But none the less we are getting close:

    [​IMG]

    Until:
    [​IMG]

    Racing carbs, they took the floats off to save weight. :rofl

    (inside joke)

    Many thanks to Dagwood, Direwolf, Helikron, Twisty Sister and Beth for the garage time.

    Floats are on the way from Spec II, I'll update then.
    #1
  2. klp

    klp Been here awhile

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    What is that nicely welded aluminum thingy behind the head?
    #2
  3. MayerMR

    MayerMR Been here awhile

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    Looks pretty great! Any pics of the engine rebuild? Any signs of what caused the failure in the first place?
    #3
  4. Mike Butt

    Mike Butt Agent Provocateur

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    It's some sort of period equalization pipe for the carbs.
    #4
  5. Mike Butt

    Mike Butt Agent Provocateur

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    I had a local shop do the rebuild. It failed so badly that it literally whipped out the bottom end too.
    #5
  6. welder

    welder Long timer

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    Actually its called a boost bottle. Someone pls. correct me if I'm wrong but I believe it takes unspent air /fuel mixture and stores it until it is needed on the next intake stroke.
    #6
  7. Mike Butt

    Mike Butt Agent Provocateur

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    Think it works?
    #7
  8. Aaron_D

    Aaron_D Adventurer

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    They're supposed to help in the low-end and mid-range.
    #8
  9. LongWays

    LongWays Skiing up a hill...

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    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/pE0Z1T9sqhM&amp;hl=en_US&amp;fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/pE0Z1T9sqhM&amp;hl=en_US&amp;fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

    :lol3
    #9
  10. Pigford

    Pigford British

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    Boost bottles were introduced on the early LC's - they are intended to even out the pulses for better low/mid range as Welder says :wink:

    Can't do much harm, but not ever really proven 100%

    I had a mildly tweeked RD400 - and did the std carb mods - drill out air jet on intake side & fitted the Y tube with a TDM850 K&N filter, etc ....

    [​IMG]

    But ny favourite was back in the day (late 70's) - my RD250 with 400 race barrels and 350 pistons - that thing flew - had 220 main jets in std carbs, would power wheely in 3rd - but coz std gearing still only do 100 mph :clap

    BEFORE

    [​IMG]

    In action in the FRONT -

    [​IMG]

    AFTER THE MODIFYING - :evil

    [​IMG]
    #10
  11. FLYING EYEBALL

    FLYING EYEBALL out of step

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    Spotted this at the Swiss earlier this evening...

    [​IMG]
    #11
  12. jb_supermoto

    jb_supermoto User

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    Sweet.. An RD thread.. keep it comin!
    #12
  13. Mike Butt

    Mike Butt Agent Provocateur

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    Fuck yeah. :clap
    #13
  14. Mark G

    Mark G Sacrificial Anode

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    It's a Helmholtz resonator http://en.wikipedia.org/wiki/Helmholtz_resonance

    They have a measurable but small effect. They are tuned for a specific RPM - just like an expansion chamber. If all the little goodies are tuned for the same RPM - look out :eek1. If they are tuned for slightly different RPM, the power gets spread around a little bit (in a two stroke "spread around" is relative) :D.
    #14
  15. Inane Cathode

    Inane Cathode Cheated Anion

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    YICS before it was YICS.

    Otherwise known as the yamaha vacuum leak induction system.
    #15
  16. MODNROD

    MODNROD Wheat and Sheep

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    :rofl :rofl :rofl
    My DS7 back in the day had a few of them......
    #16
  17. Mike Butt

    Mike Butt Agent Provocateur

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    Got the floats in the mail today. :D
    #17
  18. DireWolf

    DireWolf Knees in the Breeze

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    More before pics:

    [​IMG]

    [​IMG]

    [​IMG]

    :freaky
    #18
  19. LongWays

    LongWays Skiing up a hill...

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    That'll buff right out :evil
    #19
  20. Mike Butt

    Mike Butt Agent Provocateur

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    We did manage to save some of the gasket material.
    #20