Air Gas Mix

Discussion in 'Mechanic and Repair' started by vipermanz, Jul 14, 2001.

  1. vipermanz

    vipermanz LawnSite Bronze Member
    Messages: 1,773

    Is it possible for an engine to get TOO much gas?
    If so would that make the engine run poorly?
    Could all my problems be in the governer assembly?
    Do i ask to many questions?!:D
  2. Mr.Ziffel

    Mr.Ziffel LawnSite Senior Member
    Messages: 291

    I'm just a hack at this stuff, but...isn't the fuel/air mix controlled by the carburetor? Assuming the air/oxygen adjustment is the same, then I believe it's Rich = more fuel/air mix - Lean = less fuel/air mix.

    I think the governor in most cases I'm familiar with controls the throttle cable. I'm not familiar with how electronics/fuel injection, etc., stuff works so that wouldn't apply to my statement.

    Look to your carb adjustment first before you mess with the governor is the extent of my advice. Good luck, Will M>
  3. sdwally

    sdwally LawnSite Senior Member
    Messages: 386

    Air/Fuel mixture:
    On most engines that are not fuel injected, there are two adjustment screws. The larger one adjusts the mixture ratio at mid to high rpms. The smaller one is the mixture ratio for at idle. Once the idle screw is adjusted for the engine to run smooth at about 900 to 1000 rpm. There should also be a screw to set idle speed(sometimes on the throttle plate attached to the carb). This screw is external of the carb. It sets the closed position of the butterfly valve in the carb at idle. Setting idle requires adjustment of both of these screws. The larger screw which sets the mixture at high rpm is adjusted by the following.
    1. Screw all the way in(not tight, can damage jetting).
    2. Back screw out 1 1/2 turns.
    3. Start engine and run at full throttle.
    4. Open screw slowly until engine starts to load down with fuel.
    5. Close screw slowly until engine runs smooth.
    6. Return engine to idle.
    7. Find governer lever and manually push engine to full throttle(Do not hold it at full throttle). The engine should accelerate quickly and crisply. If it responds slowly close screw slightly. If the engine bogs down open screw slightly. Test response again. Larger engines(2 cylinders) respond slower than smaller engines.

    Some carbs have fixed jets, no adjustments. Lack of power or performance can be a result of plugged jets. This means tearing down the carb and clean all passages with carb cleaner and compressed air. Carbs that are really gummed up need to set in carb dip for awhile(nasty stuff, use rubber gloves). Before use carb dip remove all rubber parts from the carb. Carb dip is safe on metal and plastic parts only! It will ruin rubber and remove any paint! Carb dip normally comes in a 5 gallon bucket with a strainer, however I have seen it in 1 gallon cans with no strainer.

    Fuel Injection is regulated by a processor and sensors. To diagnose problems with these systems you'll need an engine manual and most of the time a diagnostic scanner to attach to the engine. Unless you a really large company, leave it to the dealers mechanics. However most FI problems exsist in the connectors, especially if they are not waterproof. Most vehicle computers are replaced by mistake when it just was a bad terminal connection at the computer. Thats why aftermarket computers are really cheap. I was told that about 93% of computer replace are not bad, however the terminals were just dirty and needed to be cleaned.

    Governers regulate the high engine speed mainly under a load. Refer to engine engine manual to adjust governers.

    Chilton has a book on most small engines. It not as good a OEM book, however covers all the basic adjustments and specs for many different brands of engines.
  4. vipermanz

    vipermanz LawnSite Bronze Member
    Messages: 1,773

    i turned it in 1 1/2 turns and it really runs alot better,
    i figured it was possible to "choke it out", i guess that would explain the excessive smoke!

    Thanks for your help!!!!!!!:)
  5. vipermanz

    vipermanz LawnSite Bronze Member
    Messages: 1,773

    Runnin' Fine after the carb adjustment:blob3:
    Thanks Again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:D
  6. Robert Doubrava

    Robert Doubrava LawnSite Senior Member
    Messages: 342

    when you turn the carb adjustment screw clockwise, the RPMs decrease. when you turn the screw conter-clockwise, the RPMs increase. just dont turn it too much.:blob3:

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