Dellorto SHA Clone - Fuel circuit schematic

Discussion in 'Performance Mods' started by Fabian, Nov 17, 2009.

  1. Fabian

    Fabian Well-Known Member

    G'day all

    I've purchaseda Rock Solid Engines 70cc motor with the Optional Dellorto carburettor.

    From what i now understand, it appears to be a Dellorto SHA clone carburettor with an adjustable mixture screw in addition to the idle speed screw.

    I can't find a fuel schematic for the carby anywhere, as i need to know how the mixture screw regulates fuel flow, i.e. is it a simple stop type valve like R/C glow engines or does it effect a certain percentage of throttle opening using a seperate fuel circuit connected to the mixture screw.
    I can't see how the mixture needle would be able to regulate fuel flow through the entire range of throttle opening but more as a method of limiting maximum fuel flow at maximum throttle openings.
    Maybe i'm wrong in my assessment.

    There are no markings on the carby to show the manufacturers name or model number, apart from the fact that it looks identical to a Dellorto SHA.

    I would be grateful for any advise.


  2. 210061741

    210061741 Guest

    Boy not too much help here.
    Pirate Cycles has a diagram to show how to connect.
    If it is the same carb.
    I know iv'e seen the schematic your looking for i just don't know where.
    I'm thinking a vendor or maybe even the dellorto site.

    But IDK
  3. arceeguy

    arceeguy Active Member

    The mixture needle controls low speed mixture, it has little effect at WOT. Mid and High range are controlled by fixed jets.
  4. AussieSteve

    AussieSteve Active Member

    What arceeguy said - the mixture screw is an idle mixture screw. Generally, on most types of carb, if you screw it all the way in until it gently bottoms, then out 1 1/4 to 1 1/2 turns, it'll be in the ballpark for starting. Any further adjustment should be done when the engine is at normal operating temperature.
    (It's a good idea to remember the original screw position so you can put it back how it was if necessary.)
    I was going to buy one of the Dellorto carbs from Tony myself, but I'm after more bottom-end and he reckons that the standard carb is better for that, jetted accordingly.
    Incidentally, many people claim that the standard main jet in an NT carby is 0.7, but Tony tells me that it's actually 0.79, so those people 'jetting up' to 0.76 are actually jetting down and leaning their mixture to get their engines to run better.
    (I ordered my billet head today - can't wait for it to arrive.)
    Boys never grow up, they just get better toys.
    ... Steve
  5. Fabian

    Fabian Well-Known Member

    You will love the Billet Cylinder Head - it's a reflection of what Tony's full Billet Engine and digital/programmable fuel injection and ignition system will look like when released next January.