What is jetting on a motorcycle? Dyno Jet?

I noticed when people show off thier changed exhausts on their bikes, people always ask "did you re jet it?" What is jetting and what does it do?

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  • 1 decade ago
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    Jets are small tubes located in the carburetor that connect the venturi (the part of the carb that the air flows through) to the fuel bowl located on the bottom of the carb. As air flows through the venturi, it creates a vacuum which draws fuel up into the incoming air, creating the air/fuel mixture.

    Jets can be changed to larger or smaller diameters, allowing more or less fuel to be mixed into the incoming air. You have to disassemble the carb to change the jets, you can remove them with a screwdriver or small wrench in most cases, although some jets are pressed in and cannot be changed. It just depends on the brand and model of the carb.

    Dyno Jet is a company that makes kits for carbs that include a variety of jet sizes, different jet needles (a toothpick sized item that acts as a valve for the main jet), different springs for the diaphragm, etc.

    People buy exhaust systems that flow more air out of the heads, creating a larger vacuum to draw in the fresh fuel/air mixture from the carb. Now a greater volume of air is flowing through the carb, but often the small diameter of the jet is not enough to allow adequate fuel to mix with the incoming air, creating a "lean" condition. Lean means that there is not enough fuel in the air/fuel mixture, rich is just the opposite. Changing a jet to a larger size will allow more fuel into the venturi to compensate for the additional air flow made possible by the new exhaust system.

  • 1 decade ago

    Motorcycles are tuned at the factory to run with the stock breathers and exhaust pipes. any time you change a component, breather or pipe, you change that setting. if the change is minor, such as changing the pipes, or the breather to a more open configuration, re jetting the carb may not be necessary. when both are changed, the gas-air mix becomes too lean, and the bike runs poorly, usually backfiring out of the carb. this is when the re jetting needs to be done, to allow more gas to the engine. usually the slow jet, or smaller jet will be replaced and sometimes the high speed, or main jet is also replaced.

    on fuel injected bikes, the computer system will have to be re mapped, or re-programed, since these fuel systems don't have jets. or carbs.

  • Anonymous
    4 years ago

    Jetting A Carb

  • Anonymous
    5 years ago

    This Site Might Help You.

    RE:

    What is jetting on a motorcycle? Dyno Jet?

    I noticed when people show off thier changed exhausts on their bikes, people always ask "did you re jet it?" What is jetting and what does it do?

    Source(s): jetting motorcycle dyno jet: https://tr.im/11jYR
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  • 1 decade ago

    Note that the Dyno jet "jets" do not correspond in size to Keihin or Mikuni jets.

  • 1 decade ago

    jets are small orifices that let fuel into the manifold. The bigger the jets the more fuel, which translates to more power going into the cylinders. In order to evacuate that extra combusted fuel you need to change to a bigger exhaust system which is why people ask did you re jet when you change the exhaust.

  • Kellie
    Lv 4
    4 years ago

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    It tells you in the maunal and it tells you on the PC website. Why not look there?

  • 1 decade ago

    lean your mains

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