Carby Lean vs Rich

Discussion in '2-Stroke Engines' started by JimKamenidis, Oct 19, 2010.

  1. JimKamenidis

    JimKamenidis Member

    I would like some help!
    I have an ht engine and it was running fine but I thought it was a little too rich at idle so I changed the needle setting at the leanest and I think I have lost some power althought the engine still runs fine, can this be due to the leaner setting???

  2. RdKryton

    RdKryton Active Member

    Lean = Heat = Damage If I made a change that makes it run worse I would definitely change it back. The needle is for mid range and high speed not idle. Not sure which engine you have but you should have a mixture screw for the idle.
    Good luck.
    Last edited: Oct 19, 2010
  3. motorpsycho

    motorpsycho Active Member

    there is not a mix screw for the idle circuit. the idle screw only adjusts the idle speed.
    most of these engines have n.t. carbs on them which do not have air-fuel mixture screws.

    if an engine runs lean it will make more power, not less..but it will run hotter and not last as long.
    changing your needle clip WILL affect the idle, because when you set it at the leanest setting (the highest notch on the needle) you are making the needle got further down into the needle jet hole, which reduces the amout of fuel that will be pulled out of the main jet.
    changing your needle clip setting will affect the fuel-air mixture from idle to about 3/4 throttle. so if your clip was in the middle and you raised it to the top notch, your idle should have increased just by making that change. the reason the idle would increase is because you leaned out the air-fuel mixture, and more air will make it idle higher.

    at wide open throttle, the needle is out of the needle jet hole and the needle is not metering any fuel at that point. the only way you can change the lean-rich setting for w.o.t. is to change the main jet.

    it's ok to have your air-fuel mixture a little rich, as long as it's not overly rich to the point where the engine is struggling to stay running. if it's too rich you will get 4 stroking, which robs power big time. getting these carbs dialed in can be a real headache, but it can be done with main jet changes and alot of tinkering.
    Last edited: Oct 19, 2010
  4. RdKryton

    RdKryton Active Member

    I stand corrected. The carb on my Whizzer has a mixture screw and a needle. Sorry for the misinformation...

  5. JimKamenidis

    JimKamenidis Member

    I pretty much know that a leaner setting results in more rpm but what if it isn't rich enough to make power?? because I know that alot of racers enrichen their engines for more power
    (I also recently changed to an iridium plug and it's brown!)
  6. JimKamenidis

    JimKamenidis Member

    I runned a check with the choke and It won't keep running with choke on so I guess it's not so lean after all..
  7. motorpsycho

    motorpsycho Active Member

    well, you can richen the mixture to get more power, but you have to do more than just richen the mixture.
    you need higher compression, porting, polishing and stuff liek that to take advantage of a richer mixture,
    do this because the engines are race engines that have been modified...not off the shelf stock. low compression engines like these.
  8. HeadSmess

    HeadSmess Well-Known Member

    a racing tip i once over heard at the pits...

    iridium plugs make you go faster :D


    easy. they lighten your wallet drastically! :lol:

    other than lasting you for the next 50,000 km or so.....
  9. Waxxumus

    Waxxumus Member

    Actually they're guaranteed for 120,000 Miles. so. 193121 Km.
  10. butre

    butre Well-Known Member

    while you're at it, a boost bottle has the same effect